In this paper, the performance simulations of a novel ultra-compact balanced coherent photodetector for operation at a wavelength of 1.5 mu m are presented and design proposals for future fabrication processes are provided. It consists of a compact 2x2 MMI that is evanescently coupled into a germanium MSM photodetection layer. The simulations demonstrate dark current less than 10 nA, capacitance less than 20 fF, and optical bandwidth in the 10-30 GHz range. We propose utilizing the simplicity of direct wafer bonding to bond the detection layer to the output waveguides to avoid complicated epitaxial growth issues. This ultra-compact device shows promise as a high-speed, low-cost integrated silicon photonics solution for the telecommunications infrastructure.

Fotodetectores baseados em poços quânticos (QWIPs Quantum¬-Well Infrared Photodetectors) possuem inúmeras aplicações nos campos da medicina, engenharia, defesa e monitoramento meteorológico e ambiental. O espectro de absorção dos QWIPs possui alta seletividade do comprimento de onda, e esse tipo de fotodetector é a escolha atual para a fabricação de câmeras de alta resolução operando no infravermelho. Atualmente, o Brasil enfrenta uma limitação na importação desse tipo de tecnologia, imposta pelos países mais desenvolvidos, devido à possibilidade de ser usada em aplicações militares. Neste trabalho, propomos o desenvolvimento e a fabricação de novos fotodetectores baseados em transições intrabanda em poços quânticos crescidos por epitaxia de feixes moleculares sobre substratos de GaAs. O crescimento epitaxial dos poços quânticos foi investigado, e as amostras foram analisadas por fotoluminescência (PL, Photoluminescence) de modo a verificarmos a qualidade e reprodutibilidade das heteroestruturas produzidas. O cálculo dos níveis de energia e das funções de onda dos poços quânticos foi feito por meio da implementação numérica do método da matriz de transferência [21] no software Mathematica. Esse método também foi aplicado ao cálculo autoconsistente envolvendo a dopagem da estrutura. A partir dos valores das energias de confinamento e das funções de onda obtidas pelo programa, algumas grandezas físicas puderam ser estimadas tais como o coeficiente de absorção teórico, a corrente de escuro e o ruído. Também foi implementado um modelo para o cálculo dos níveis de energia de uma impureza hidrogenóide dentro de um poço quântico de GaAs com barreiras de AlGaAs. Acredita-se que esse sistema possua melhores características de ruído em relação a um QWIP comum, no qual as impurezas estão completamente ionizadas [25] [26] [27]. O processamento das amostras para a fabricação dos fotodetectores foi desenvolvido e otimizado, e envolveu técnicas convencionais de fotolitografia, para a formação por ataque químico das estruturas de pequenos fotodetectores singelos sobre a amostra, e a deposição de filmes finos metálicos para a obtenção dos contatos (ôhmicos). Foram desenvolvidas e implementadas várias técnicas de caracterização para determinar o comprimento de onda de operação, a responsividade, o ruído intrínseco, e a corrente no escuro (dark current) dos QWIPs fabricados. No inicio deste projeto de doutorado, nenhuma das técnicas de caracterização estava disponível no laboratório. A caracterização completa dos QWIPs foi feita medindo-se o coeficiente de absorção e a resposta espectral por espectroscopia no infravermelho por transformada de Fourier (FTIR), a fotocorrente foi medida com um corpo negro, a corrente de escuro usando curvas I-V, e o ruído com um analisador de espectros. As medidas foram realizadas em função da voltagem de polarização (bias) aplicada, em diferentes valores de temperatura. Foram crescidas várias amostras de QWIPs, para absorção nas janelas atmosféricas de 3m a 5m e de 8m a 12m. A curva de absorção de cada amostra foi medida, e a caracterização optoeletrônica completa foi realizada em dois desses QWIPs, para a região de 8m a 12m. O melhor resultado foi obtido em um QWIP com o pico de absorção em 9,3m, que apresentou detectividade de 5×1010 cm.Hz1/2/W para 10K e 4×109 cm.Hz1/2/W para 70K. / Photodetectors based on quantum wells (QWIPs Quantum-Well Infrared Photodetectors) have numerous applications in the fields of medicine, engineering, defense, meteorology and environmental monitoring. The absorption spectrum of QWIPs has high wavelength selectivity, and this type of photodetector is the current choice for the fabrication of high-resolution cameras operating in the infrared. Currently, Brazil faces restrictions to import such a technology, imposed by the developed countries, due to its possibility of being used in military applications. In this thesis, we propose the development and optimization of photodetectors based on intraband transitions in quantum wells grown by molecular beam epitaxy (MBE) on GaAs substrates. The epitaxial growth of the quantum wells was investigated, and the samples were analyzed by photoluminescence (PL) to verify the quality and reproducibility of the heterostructures. The calculations of the energy levels and wavefunctions of the quantum wells were done by numerical implementation of the transfer matrix method [21] in the Mathematica software. This method was also applied to the self-consistent calculations involving the doping of the structures. From the values of the confinement energies, the wave functions could be obtained as well, and some physical quantities such as the theoretical absorption coefficient, the dark current and noise could be estimated. A model was also developed for the calculation of the energy levels of a hydrogenoid impurity inside a GaAs quantum well with AlGaAs barriers. It is believed that this system could have better noise characteristics when compared to a common QWIP in which the impurities are completely ionized [25] [26] [27]. The sample processing for the manufacture of the photodetectors was developed, optimized, and involved conventional photolithography techniques to define the physical size of the devices (followed by wet etching) as well as metallic film deposition to obtain ohmic contacts . Several characterization techniques were developed and installed to determine the wavelength of operation, the responsivity, the intrinsic noise and the dark current of the QWIPs manufactured in our laboratory. When this PhD project started, none of the characterization techniques was available in the lab. A complete set of experimental data was achieved by measuring the absorption coefficient and the spectral response by Fourier transform infrared spectroscopy (FTIR), the photocurrent using a blackbody, the dark current using I-V curves, and the noise with a spectrum analyzer. The measurements were performed as a function of the bias voltage at different temperatures. Several QWIPs samples were grown for absorption in the atmospheric windows from 3m to 5m and from 8m to 12m. The absorption curve of each sample was measured, and full characterization was performed on two QWIPs, in the region of 8m to 12m. The best results were obtained in a QWIP with peak absorption at 9.3m, which showed a detectivity of 5×1010 cm.Hz1/2/W at 10K and 4×109 cm.Hz1/2/W at 70K.

Fotodetectores baseados em poços quânticos (QWIPs Quantum¬-Well Infrared Photodetectors) possuem inúmeras aplicações nos campos da medicina, engenharia, defesa e monitoramento meteorológico e ambiental. O espectro de absorção dos QWIPs possui alta seletividade do comprimento de onda, e esse tipo de fotodetector é a escolha atual para a fabricação de câmeras de alta resolução operando no infravermelho. Atualmente, o Brasil enfrenta uma limitação na importação desse tipo de tecnologia, imposta pelos países mais desenvolvidos, devido à possibilidade de ser usada em aplicações militares. Neste trabalho, propomos o desenvolvimento e a fabricação de novos fotodetectores baseados em transições intrabanda em poços quânticos crescidos por epitaxia de feixes moleculares sobre substratos de GaAs. O crescimento epitaxial dos poços quânticos foi investigado, e as amostras foram analisadas por fotoluminescência (PL, Photoluminescence) de modo a verificarmos a qualidade e reprodutibilidade das heteroestruturas produzidas. O cálculo dos níveis de energia e das funções de onda dos poços quânticos foi feito por meio da implementação numérica do método da matriz de transferência [21] no software Mathematica. Esse método também foi aplicado ao cálculo autoconsistente envolvendo a dopagem da estrutura. A partir dos valores das energias de confinamento e das funções de onda obtidas pelo programa, algumas grandezas físicas puderam ser estimadas tais como o coeficiente de absorção teórico, a corrente de escuro e o ruído. Também foi implementado um modelo para o cálculo dos níveis de energia de uma impureza hidrogenóide dentro de um poço quântico de GaAs com barreiras de AlGaAs. Acredita-se que esse sistema possua melhores características de ruído em relação a um QWIP comum, no qual as impurezas estão completamente ionizadas [25] [26] [27]. O processamento das amostras para a fabricação dos fotodetectores foi desenvolvido e otimizado, e envolveu técnicas convencionais de fotolitografia, para a formação por ataque químico das estruturas de pequenos fotodetectores singelos sobre a amostra, e a deposição de filmes finos metálicos para a obtenção dos contatos (ôhmicos). Foram desenvolvidas e implementadas várias técnicas de caracterização para determinar o comprimento de onda de operação, a responsividade, o ruído intrínseco, e a corrente no escuro (dark current) dos QWIPs fabricados. No inicio deste projeto de doutorado, nenhuma das técnicas de caracterização estava disponível no laboratório. A caracterização completa dos QWIPs foi feita medindo-se o coeficiente de absorção e a resposta espectral por espectroscopia no infravermelho por transformada de Fourier (FTIR), a fotocorrente foi medida com um corpo negro, a corrente de escuro usando curvas I-V, e o ruído com um analisador de espectros. As medidas foram realizadas em função da voltagem de polarização (bias) aplicada, em diferentes valores de temperatura. Foram crescidas várias amostras de QWIPs, para absorção nas janelas atmosféricas de 3m a 5m e de 8m a 12m. A curva de absorção de cada amostra foi medida, e a caracterização optoeletrônica completa foi realizada em dois desses QWIPs, para a região de 8m a 12m. O melhor resultado foi obtido em um QWIP com o pico de absorção em 9,3m, que apresentou detectividade de 5×1010 cm.Hz1/2/W para 10K e 4×109 cm.Hz1/2/W para 70K. / Photodetectors based on quantum wells (QWIPs Quantum-Well Infrared Photodetectors) have numerous applications in the fields of medicine, engineering, defense, meteorology and environmental monitoring. The absorption spectrum of QWIPs has high wavelength selectivity, and this type of photodetector is the current choice for the fabrication of high-resolution cameras operating in the infrared. Currently, Brazil faces restrictions to import such a technology, imposed by the developed countries, due to its possibility of being used in military applications. In this thesis, we propose the development and optimization of photodetectors based on intraband transitions in quantum wells grown by molecular beam epitaxy (MBE) on GaAs substrates. The epitaxial growth of the quantum wells was investigated, and the samples were analyzed by photoluminescence (PL) to verify the quality and reproducibility of the heterostructures. The calculations of the energy levels and wavefunctions of the quantum wells were done by numerical implementation of the transfer matrix method [21] in the Mathematica software. This method was also applied to the self-consistent calculations involving the doping of the structures. From the values of the confinement energies, the wave functions could be obtained as well, and some physical quantities such as the theoretical absorption coefficient, the dark current and noise could be estimated. A model was also developed for the calculation of the energy levels of a hydrogenoid impurity inside a GaAs quantum well with AlGaAs barriers. It is believed that this system could have better noise characteristics when compared to a common QWIP in which the impurities are completely ionized [25] [26] [27]. The sample processing for the manufacture of the photodetectors was developed, optimized, and involved conventional photolithography techniques to define the physical size of the devices (followed by wet etching) as well as metallic film deposition to obtain ohmic contacts . Several characterization techniques were developed and installed to determine the wavelength of operation, the responsivity, the intrinsic noise and the dark current of the QWIPs manufactured in our laboratory. When this PhD project started, none of the characterization techniques was available in the lab. A complete set of experimental data was achieved by measuring the absorption coefficient and the spectral response by Fourier transform infrared spectroscopy (FTIR), the photocurrent using a blackbody, the dark current using I-V curves, and the noise with a spectrum analyzer. The measurements were performed as a function of the bias voltage at different temperatures. Several QWIPs samples were grown for absorption in the atmospheric windows from 3m to 5m and from 8m to 12m. The absorption curve of each sample was measured, and full characterization was performed on two QWIPs, in the region of 8m to 12m. The best results were obtained in a QWIP with peak absorption at 9.3m, which showed a detectivity of 5×1010 cm.Hz1/2/W at 10K and 4×109 cm.Hz1/2/W at 70K.

The electronic properties of amorphous materials are greatly affected by the density of localized states in the mobility gap of these materials. The exact shape of the density of states (DOS) distribution in amorphous selenium (a-Se) is still unresolved despite decades of research. One of the most commonly employed methods to investigate charge transport properties in high resistivity materials is time-of-flight (TOF) transient photoconductivity experiment. The TOF transient photoconductivity technique is used to measure the induced photocurrent in the external circuit when the sample is photoexcited. Information pertaining to carrier mobility and other carrier parameters are deduced from the shape of the photocurrent. The investigation of the charge transport phenomenon is well known to be a complicated task. Monte Carlo (MC) simulation method has become a standard method for carrier transport studies in amorphous materials. The purpose of this research work is to develop a Monte Carlo simulation model for charge transport in typical TOF transient photoconductivity experiment to investigate the DOS distribution in a-Se. The MC simulations were first performed for relatively simpler models for which theoretical and analytical solutions were available. The MC model developed here is based on simulating the drift of carriers resulting from photogeneration, subject to the influence of an applied electric field and multiple trapping events. The free drift time of photocarriers and their dwell time in the traps are stochastic in nature, in accordance with the probabilities of these events. Electron time-of-flight transient photocurrents were calculated in amorphous selenium as a function of the electric field. The distribution of localized states (DOS) in a-Se has been investigated by comparing the experimentally measured and calculated transient photocurrents. The analysis of multiple-trapping transport has been done by the discretization of a continuous DOS. The DOS distribution has been optimized to produce the best agreement between the calculated and measured transient photocurrents. The resulting DOS has distinct features: A first peak at ~0.30 eV below Ec with an amplitude ~1017 eV1 cm3, a second small peak (or shoulder) at 0.450.50 eV below Ec with an amplitude 10141015 eV1 cm3, and deep states with an integral concentration 10111014 cm3 lying below 0.65 eV, whose exact distribution could not be resolved because of the limitations of the available experimental data. The density of states (DOS) distribution in the vicinity of the valence band mobility edge in vacuum coated a-Se films has been investigated by calculating the MC hole transient photocurrents at different temperatures, and also the dependence of the drift mobility on the temperature and field. The calculated TOF transient photocurrents were compared with experimental data published elsewhere. It is shown that, analogous to electron transport in a-Si:H, the DOS near Ev is a featureless, monotonically decreasing distribution in energy up to Ev + 0.4 eV, without the 0.28 eV peak near the valence band which was thought to control the hole drift mobility. Such a DOS was able to account for hole TOF data reported previously by several authors to date.

The electronic properties of amorphous materials are greatly affected by the density of localized states in the mobility gap of these materials. The exact shape of the density of states (DOS) distribution in amorphous selenium (a-Se) is still unresolved despite decades of research. One of the most commonly employed methods to investigate charge transport properties in high resistivity materials is time-of-flight (TOF) transient photoconductivity experiment. The TOF transient photoconductivity technique is used to measure the induced photocurrent in the external circuit when the sample is photoexcited. Information pertaining to carrier mobility and other carrier parameters are deduced from the shape of the photocurrent. The investigation of the charge transport phenomenon is well known to be a complicated task. Monte Carlo (MC) simulation method has become a standard method for carrier transport studies in amorphous materials. The purpose of this research work is to develop a Monte Carlo simulation model for charge transport in typical TOF transient photoconductivity experiment to investigate the DOS distribution in a-Se. The MC simulations were first performed for relatively simpler models for which theoretical and analytical solutions were available. The MC model developed here is based on simulating the drift of carriers resulting from photogeneration, subject to the influence of an applied electric field and multiple trapping events. The free drift time of photocarriers and their dwell time in the traps are stochastic in nature, in accordance with the probabilities of these events. Electron time-of-flight transient photocurrents were calculated in amorphous selenium as a function of the electric field. The distribution of localized states (DOS) in a-Se has been investigated by comparing the experimentally measured and calculated transient photocurrents. The analysis of multiple-trapping transport has been done by the discretization of a continuous DOS. The DOS distribution has been optimized to produce the best agreement between the calculated and measured transient photocurrents. The resulting DOS has distinct features: A first peak at ~0.30 eV below Ec with an amplitude ~1017 eV1 cm3, a second small peak (or shoulder) at 0.450.50 eV below Ec with an amplitude 10141015 eV1 cm3, and deep states with an integral concentration 10111014 cm3 lying below 0.65 eV, whose exact distribution could not be resolved because of the limitations of the available experimental data. The density of states (DOS) distribution in the vicinity of the valence band mobility edge in vacuum coated a-Se films has been investigated by calculating the MC hole transient photocurrents at different temperatures, and also the dependence of the drift mobility on the temperature and field. The calculated TOF transient photocurrents were compared with experimental data published elsewhere. It is shown that, analogous to electron transport in a-Si:H, the DOS near Ev is a featureless, monotonically decreasing distribution in energy up to Ev + 0.4 eV, without the 0.28 eV peak near the valence band which was thought to control the hole drift mobility. Such a DOS was able to account for hole TOF data reported previously by several authors to date.

<p>The visible wavelength range has proven to be a useful spectral window for observing biophotonic events such as absorption in materials (oxy-hemoglobin and deoxy-hemoglobin), light scattering in biological tissue, and biochemical and fluorescence reactions. Diffuse reflectance spectroscopy (DRS) is a technique that utilizes the diffuse reflectance spectra from turbid media (e.g. biological tissue) to quantify the optical properties (e.g. absorption and scattering) of those media. DRS in the visible wavelength range can be utilized to optically differentiate between healthy and cancerous tissue, and thus has applications in intra-operative tumor margin assessment. </p><p>The footprint of conventional DRS systems used for intra-operative tissue margin assessment prohibits their widespread use inside the surgical suite, where space is at a premium. Conventional quantitative DRS imaging systems utilize unwieldy fiber probes, cooled CCD cameras, and imaging spectrographs for imaging tissue margins. These system components not only increase system size, limiting their use inside the surgical suite, but also limit imaging resolution, imaging speed, and increase overall system cost. </p><p>Silicon is an attractive candidate for the development of compact, customized photodetector elements for biophotonic imaging applications such as intra-operative tumor margin assessment using DRS. This thesis deals with the design and development of a customized DRS imaging probe composed of custom silicon imaging arrays for intra-operative breast tumor margin assessment. The first generation of the customized imaging probe consisted of a 4x4 array of annular epitaxial Si pn junction photodiodes (PDs) with a measured responsivity of 0.28 A/W - 0.37 A/W for &#955;= 470 nm - 600 nm, and a measured dark current density of 1.456 nA/cm2 - 4.48 nA/cm2. The imaging array was used to detect diffuse reflectance when placed in direct contact with tissue. A quartz light delivery tube coupled to a xenon lamp was optimized to deliver light to the tissue through the holes of the annular imaging array across a 256 mm2 imaging area. The pixel-to-pixel spacing in the imaging array was 4.5 mm, the highest resolution reported to date for a multi-pixel DRS probe. This resolution was limited by pixel-to-pixel optical crosstalk, which was theoretically calculated and experimentally characterized, to validate the theoretical model for future designs. This first generation probe was successfully tested on diffuse reflectance standards, tissue-mimicking phantoms, animal tissue, and human breast tissue, and yielded an SNR of 30 dB - 55 dB on all measured specimens. </p><p>The next generation of the customized imaging probe consisted of a 4x4 array of annular thin-film Si pn junction PDs heterogeneously bonded to a transparent Pyrex substrate, to enable integration with a guided wave light delivery system. The 4x4 thin-film PD array design and development was prototyped using a 1x2 thin-film PD array heterogeneously bonded to a Pyrex substrate. The responsivity and dark current of the thin-film PDs in the 1x2 array were measured to be 0.19 A/W - 0.34 A/W for &#955;= 470 nm - 600 nm and 0.63 nA/cm2, respectively. The process for the 1x2 thin-film PD array was scaled to fabricate a 4x4 array of thin-film PDs for DRS, and the 4x4 array was optically and electrically characterized. These heterogeneously bonded thin-film single crystal Si PDs have the highest uncooled responsivity to dark current density ratio (greater than 0.30 - 0.54 cm2/nW for &#955;= 470 nm - 600 nm) reported to date, to the best of our knowledge. The 1x2 array of thin-film PDs were also heterogeneously bonded to a flexible substrate without any degradation in PD optical and electrical characteristics, opening the door towards conformal tissue imaging.</p> / Dissertation

Photodetectors are semiconductor devices capable of converting optical signals into electrical signals. There is a wide range of applications for photodetectors such as fiber optics communication, infrared heat camera sensors, as well as in medical and military equipment.Nanowires are thin needle-shaped structures consisting of semiconductor materials such as gallium arsenide (GaAs), indium phosphide (InP) or silicon (Si). They are ideally suited for sensitive photodetectors with low noise due to their small size, well-controlled crystal structure, and composition tunability, as well as the possibility to fabricate them monolithically on silicon.In this thesis, Fourier Transform Infrared (FTIR) Spectroscopy was used to investigate the optical characteristics of InP nanowire-based n+-i-n+ photodetectors with 20 embedded InAsP quantum discs in each InP nanowire. The spectrally resolved photocurrent was measured and analyzed at different angles of incidence. Also, detailed current-voltage characteristics in dark and under illumination were recorded and analyzed.Summarized, the samples showed very good I-V performance with low dark leakage currents. The photocurrent scales with the numbers of nanowires, from which we conclude that most of the photocurrent is generated in the nanowires. Spectrally resolved photocurrent data, recorded at room-temperature, shows strong absorption in the near-infrared region with interesting peaks that reveal, the underlying optical processes in the substrate and nanowires.

Nesse trabalho utilizamos um modelo analítico para avaliar o desempenho de estruturas semicondutoras contendo pontos quânticos que servem de base para a fabricação de fotodetectores que operam na faixa do infravermelho. O desempenho desses dispositivos foram avaliados através da corrente no escuro e da detectividade. Os trabalhos existentes na literatura, baseados neste modelo, não consideram a de­ pendência da estrutura eletrônica do ponto quântico com suas dimensões. Desta forma, neste trabalho, analisamos o comportamento da corrente no escuro e da de­tectividade em função de vários parâmetros que definem a estrutura da amostra, levando em consideração as dimensões dos QDs. Nossos resultados mostraram quais parâmetros devemos ajustar para fazer fotodetectores: (1) que contenham a maior densidade de QDs com dimensões compatíveis com a energia de ionização desejada; (2) que maximizam o desempenho do dispositivo e (3) minimizam o ruído do mesmo. / In this work we used an analytical model to calculate the dark current and the detectivity of infrared photodetectors based on InAs quantum dots semiconductor heterostructures. The existing works reported in the literature based on this analytical model do not take into account the electronic structure of the QD in the calculations. In this way, in the present work, we took into account the QD dimensions when we analized the dependence of the dark current and the detectivity on the parameters which define the sample structure. Our findings show which parameters must be adjusted in order to obtain photodetectors with: (1) the larger density of QDs with dimensions compatible with the wanted ionization energy; (2) that maximize the performance; (3) and that minimize the noise of the devices.

The ability of Mercuric Iodide (HgI2) to function as a highly efficient radiation detector at room temperature has generated great interest and has triggered further studies on this difficult material. This property is expected to enable significant enhancements to a far-ranging variety of applications and systems. HgI2 devices have shown superior performance at room temperature compared to elemental Si or Ge devices, which require to be cooled down to liquid nitrogen temperature when used as nuclear radiation detectors. While substantial studies have been conducted on single crystal HgI2, polycrystalline HgI2 remains a comparatively less studied form of this material. The primary use of HgI2 is as a direct radiation detector. It can also be used in applications with a scintillator intermediate to generate visible light from incident nuclear radiation. Hence its response to visible light can be used to study the electronic properties of HgI2 polycrystalline films. The films are deposited on TEC-15 LOF glass with a Tin Oxide(Sn02) coating which acts as the growth surface. It also acts as the front contact with Palladium (Pd) being the back contact. Wire leads are attached to the palladium for electrical contact. The deposited films are circular in shape with a diameter of 2.5cm with thickness ranging from 50 to 600µm. A maximum of 7 devices are contacted at various points on every film. For the measurements documented in this thesis, a tungsten-halogen lamp and an Oriel 1/4m grating monochromator are used as a light source. The incident flux on the sample is determined using a Si photodiode as reference. Device performance for both single crystal as well as polycrystalline films is documented. We have attempted to identify a set of optimum growth parameters using these measurements. For a film to be considered favorably, not only should the individual devices show high quantum efficiencies and low dark currents, but the response of all devices on the same film should be uniform. A number of films are studied and the optimum film deposition conditions are commented upon. A powerful semiconductor device simulation tool, MEDICItm, is used to simulate the photoresponse of these films. The simulations are compared to the measurements and the transport and light absorption parameters of the polycrystalline films are determined.

Quantum well infrared photodetectors (QWIP) utilize quantum wells of large bandgap materials to detect infrared radiation. When compared to conventional low bandgap LWIR photodetectors, the QWIP technology offers largest format thermal imagers with much better uniformity. The theoretical part of this study includes the development of a QWIP ensemble Monte-Carlo simulator. Capture paths of electrons to quantum wells are simulated in detail. For standard AlGaAs/GaAs QWIPs, at medium and high E-fields L valley quantum well (QW) is a trap for electrons which causes higher capture probability when compared with InP/InGaAs and GaAs/InGaAs QWIPs. The results suggest that high photoconductive gain observed in InP/InGaAs and GaAs/InGaAs QWIPs is not due to good transport properties of binary barrier material but due to higher &amp / #61511 / -L valley energy separation. The experimental part of the study includes the fabrication and characterization of InP/InGaAs and InP/InGaAsP QWIPs and 640x512 FPAs with the main objective of investigating the feasibility of these material systems for QWIPs. The InP/InGaAs and InP/InGaAsP QWIP detectors showed specific detectivity values above 1010 cm.Hz1/2/W (70K, f/2, background limited). The devices offer higher allowable system noise floor when compared with the standard AlGaAs/GaAs QWIP technology. It is also experimentally shown that for strategic applications LWIR InP based QWIPs have advantages over the standard QWIP technology. The InP/InGaAs 640x512 QWIP FPA reached 36 mK average NETD value at 70 K with f/1.5 optics and 10 ms integration time. The InP/InGaAsP QWIP on the other hand yielded 38 mK NETD histogram peak at 70 K with f/1.5 optics and 5 ms integration time on 320x256 window of the 640x512 FPA.