The objective of this work was to design and develop a high performance field effect transistor to be suitable for monolithic integration with a photodetector for use in long wavelength optical communication systems. It was decided that the most promising type of device for this application was a junction field effect transistor (JFET), fabricated using the alloy In.53Ga.47As grown epitaxially onto an InP substrate. The requirements for such a device were that it should have high transconductance, low input capacitance, and low gate leakage current (for high receiver sensitivity), and that it should have a structure which would be easily integrated monolithically with the desired type of photodetector - an In.53Ga.47As PIN-photodiode. Although this alloy semiconductor has favourable electron transport properties, at the start of this work, high performance field effect transistors had not been realised in this material. In particular, the In.53Ga.47AS FETs that had been made at that time were characterised by low transconductance. Using a device design that incorporated many novel and efficacious features, the JFET described in this work gave results which greatly surpassed all previous (and current) published results of similar devices. This device not only showed high performance, but the novel design features also enabled a simple fabrication scheme. Having developed this very high performance discrete device, the feasibility of monolithic integration with a In.53Ga.47As PIN-photodiode was demonstrated. Although the physical size and material requirements of these two devices were very different, novel design features enabled the construction of a monolithic PIN-FET combination, in which the performance of the JFET was not compromised.

Gas source molecular beam epitaxy (GSMBE) has been used to grow InGaAs/lnP epitaxial layers in selected areas defined by SiO2-masked InP substrates, with the goal of obtaining controlled in-plane variations in the bandgap of the InGaAs wells. The ability to alter the bandgap of the semiconductor spatially over the surface in one growth procedure is desirable for integrating laser, waveguide and detector devices. To form the masked substrates, stripes (ranging in width from 2 pm to 50 pm) were opened up in SiO2 by standard photolithography. The crystal growths were carried out at various substrate temperatures (ranging from 460 °C to 510 °C) and arsenic fluxes (V/lll ratios ranging from 1.2 to 3.4). The properties of the epitaxial layers were investigated by using such analytical techniques as photoluminescence, electroluminescence and transmission electron microscopy (TEM). Photoluminescence measurements performed on waveguide stripes of decreasing width reveal an increasing red-shift of the e1-hh1 transition in InGaAs wells. The maximum red-shift occurred when growing at a high substrate temperature and a low arsenic flux. For example, a decrease in slit width from 50 pm to 10 pm resulted in a 25 meV shift of the photoluminescence peak. From cross-sectional TEM measurements, the wavelength shift observed can be attributed primarily to an increase in thickness of the InGaAs well, due to incorporation of additional indium and gallium migrating from the material on the masked regions. The interfaces in the centre of the stripe region are defect free; however, stacking faults and thickness variations are evident 1-2 pm from the edges. These results are confirmed by scanning photoluminescence, in which the maximum intensity occurs at the centre of the stripe and decreases to zero at the edges. Mapping of the peak wavelength across the stripe reveals a diffusion profile, with the edges being additionally red shifted by 10 nm. Reactive ion etching of the edge and the polycrystalline material results in a much improved spectral photoluminescence scan, in both increased intensity of the bandgap peak and elimination of lower energy peaks assumed to be correlated with edge effects. Finally, a stripe contact light emitting device, with a single 50 A quantum well InGaAs/lnP structure, was fabricated and electrically pumped. The device exhibited spectral peak wavelength shifts between narrow stripes (10 pm) and wide stripes (50 pm) of 22 nm, similar to the value observed by photoluminescence studies. / Thesis / Master of Engineering (ME)

Gas source molecular beam epitaxy (GSMBE) has been used to grow InGaAs/lnP epitaxial layers in selected areas defined by SiO2-masked InP substrates, with the goal of obtaining controlled in-plane variations in the bandgap of the InGaAs wells. The ability to alter the bandgap of the semiconductor spatially over the surface in one growth procedure is desirable for integrating laser, waveguide and detector devices. To form the masked substrates, stripes (ranging in width from 2 pm to 50 pm) were opened up in SiO2 by standard photolithography. The crystal growths were carried out at various substrate temperatures (ranging from 460 °C to 510 °C) and arsenic fluxes (V/lll ratios ranging from 1.2 to 3.4). The properties of the epitaxial layers were investigated by using such analytical techniques as photoluminescence, electroluminescence and transmission electron microscopy (TEM). Photoluminescence measurements performed on waveguide stripes of decreasing width reveal an increasing red-shift of the e1-hh1 transition in InGaAs wells. The maximum red-shift occurred when growing at a high substrate temperature and a low arsenic flux. For example, a decrease in slit width from 50 pm to 10 pm resulted in a 25 meV shift of the photoluminescence peak. From cross-sectional TEM measurements, the wavelength shift observed can be attributed primarily to an increase in thickness of the InGaAs well, due to incorporation of additional indium and gallium migrating from the material on the masked regions. The interfaces in the centre of the stripe region are defect free; however, stacking faults and thickness variations are evident 1-2 pm from the edges. These results are confirmed by scanning photoluminescence, in which the maximum intensity occurs at the centre of the stripe and decreases to zero at the edges. Mapping of the peak wavelength across the stripe reveals a diffusion profile, with the edges being additionally red shifted by 10 nm. Reactive ion etching of the edge and the polycrystalline material results in a much improved spectral photoluminescence scan, in both increased intensity of the bandgap peak and elimination of lower energy peaks assumed to be correlated with edge effects. Finally, a stripe contact light emitting device, with a single 50 A quantum well InGaAs/lnP structure, was fabricated and electrically pumped. The device exhibited spectral peak wavelength shifts between narrow stripes (10 pm) and wide stripes (50 pm) of 22 nm, similar to the value observed by photoluminescence studies. / Thesis / Master of Engineering (ME)

The observation of voltage-tunable plasmon resonances in the terahertz range in two dimensional electron gas (2-deg) of a high electron mobility transistor (HEMT) fabricated from the InGaAs/InP and AlGaN/GaN materials systems is reported. The devices were fabricated from a commercial HEMT wafer by depositing source and drain contacts using standard photolithography process and a semi-transparent gate contact that consisted of a 0.5 [micro]m period transmission grating formed by electron-beam lithography. Narrow-band resonant absorption of THz radiation was observed in transmission in the frequency range 10-100 cm-1. The resonance frequency depends on the gate voltage-tuned sheet-charge density of the 2deg. The fundamental and higher resonant harmonics were observed to shift towards lower frequencies with the implementation of negative gate bias. The theory of interaction of sub millimeter waves with 2deg through corrugated structure on top has been applied to calculate and understand the phenomena of resonant plasmon excitations. The observed separation of resonance fundamental from its harmonics and their shift with gate bias follows theory, although the absolute frequencies are lower by about a factor of 2-3 in InGaAs/InP system. However, calculated values match much better with AlGaN/GaN system.

<p> InGaAs/InP heterostructure nanowires (NWs) grown by gas source molecular beam epitaxy (GS-MBE) have been analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray spectroscopy (EDS). The morphology and interfacial properties of these structures have been compared to pure InP NWs and lattice-matched InGaAs!InP superlattice (SL) structures, respectively. Based on high-resolution x-ray diffraction (HRXRD) and photoluminescence (PL) measurements of the SLs a detailed structural model is proposed, consisting of strained InAsP and InGaAsP mono layers due to group-V gas switching and atomic exchange at the SL interfaces. The interfaces of the heterostructure NW s were an order of magnitude larger than those of the SLs and showed a distinct bulging morphology. Both of these characteristics are explained based on the slow purging of group-III material from the Au catalyst. Growth of lnGaAs on the sidewalls of the InP base of these wires was also observed, and occurs due to the shorter diffusion length of Ga adatoms as compared to In. </p> / Thesis / Master of Science (MSc)

Cette thèse est consacrée à l'étude des absorbants saturables à multipuits quantiques (MPQ) InGaAs/InP dopés fer. Les non-linéarités de l'absorption excitonique sont exploitées pour la régénération tout-optique du signal à 1.55mm. Un modèle théorique permet de calculer les propriétés optiques non-linéaires des puits quantiques. L'efficacité du dopage fer des MPQ à réduire le temps de relaxation de l'absorption est démontrée expérimentalement et expliquée par un modèle dynamique de la capture des porteurs par les atomes de fer. L'insertion des MPQ dopés fer en microcavité, à mode accordé à la résonance excitonique, réduit la puissance de commande optique d'un facteur 50 et permet d'obtenir un contraste de 8dB. Un tel contraste augmente la distance de propagation de plus de 1000km pour un signal numérique à 10 Gb/s. Le temps de réponse peut être réduit à une valeur record de 290fs, tout en gardant un contraste de 5dB.