There are two sections in this thesis, the first section we measured the photoluminescence (PL) spectra¡Bphotocurrent spectra and electro absorption spectra of InGaAsN single quantum well structures grown by MBE. From temperature-dependent PL spectra of InGaAsN, we observed a localized level at low temperature, and the carrier localization effect increases when the mole fraction of nitrogen increases (2.1%~3.25%). This peculiarity influences the PL peak position and the PL linewidth, and it can be improved by adequate annealing. We also obtained the activation energies about 52~59meV by Arrhenius plot and thermal quenching model. For the photocurrent spectra we observe the sub-band transition and quantum confined stark effect. From the electro-absorption spectra, we obtain the maximum absorption changes (

In this thesis, we have set up a SiO2 sputter system. The system includes sputter gun, RF power supply, RF power controller, turbo pump, quick access door, cooling water tubes, gas lines, electric circuits etc. We applied sputter techniques for quantum well intermixing (QWI) process. We can adjust the pressure, gas, RF power etc. of the sputter system to fit the best QWI conditions and then sputter a SiO2 film on the samples. The samples with multiple quantum wells were grown by our team members using molecular beam epitaxy system. After SiO2 film deposition, the samples were annealed by Rapid Thermal Process. The annealing temperatures are about 650¢J-750¢J. Following the thermal annealing, room-temperature PL measurements were used to study the blue shift and intensity change after QWI process. After our hard working, we had fixed many problems of sputter system. We have obtained useful data through many QWI experiments. Our results are listed as follows : PL intensity : We use RF power = 100W, sputter time = 5 min., annealing temperature = 675¢J, annealing time = 30 sec. PL intensity has been enhanced by 25 times. Blue shift : there is no clear blue shift.

In this thesis, we have set up a SiO2 sputter system. We applied sputter techniques for quantum well intermixing (QWI) process to increase the bandgap of the quantum well structure. The samples with multiple quantum wells were grown by our team members using molecular beam epitaxy system, and the MQW structure were grown by MOCVD. Before sputtering, some samples will use ICP to enhance the vacancy on the surface. First, we will sputter SiO2 on the surface of sample. After SiO2 film deposition, the samples were annealed by Rapid Thermal Process. And ordinary annealing were about 700¢J~800¢J. A later period, the annealing temperatures will be above 850¢J. Room-temperature PL (Photoluminescence) measurements were used to study the blue shift and intensity change after QWI process. And we will do the mesa process to measure the characteristic of optoelectronics. If the conditions are RF power = 100W, sputter time = 30 min, ICP enhance 250W for 2 min, annealing temperature = 825¢J, annealing time = 60 sec. The PL signal have a blue shift of 64nm(wavelength from 1506nm to 1444nm).When annealing temperature =700¢J, and annealing time = 60 sec, we have a blue shift of 12nm(wavelength from 1572nm to 1560nm) on the C116 sample. We do the mesa process on the MQW which contain P and it have a large blue shift. After the process, we success to compare the different between EL and Photocurrent. But the structure of samples which certain Al do not have a apparent blue shift. And the annealing temperature is too large, samples will be damaged. We think that the reason have relation to materials of the sample.

Abstract In this thesis, we have setup a photoluminescence (PL) measurement system to investigate the quantum well intermixing (QWI) effects on semiconductor multiple quantum-well (MQW) structures. The measured samples include 1.3mm and 1.55mm InGaAsP MQW laser structures grown by MOCVD, and 1.55mm InGaAlAs MQW structures by MBE. The QWI process was performed by rapid thermal annealing at 600¢J~800¢J in 1 min with a ~1300Å SiO2 layer sputtered on the semiconductor surface. Following the SiO2 sputtering and thermal annealing, room-temperature PL measurements were used to study the QWI effect. The result shows that the PL intensity is reduced for the MOCVD samples, while the MBE samples have up to 47 times increase of PL intensity. After QWI process, all the samples have a blue-shift in PL spectra. The 1.55mm InGaAsP laser structures by MOCVD have a maximum blue-shift of 34nm, and the MBE samples of 12nm after 800¢J annealing.

In this work, a quantum well intermixing(QWI) technology, called impurity free vacancy diffusion(IFVD), is used to do the bandgap engineering in an optoelectronic monolithic integration. The monolithic integration of SOAs and EAMs is taken as an example. By IFVD, the transition energy levels of EAM quantum wells can be shifted to shorter wavelength regime, while SOA quantum wells are kept the same. Therefore, the overall SOA-integrated EAM efficiency can be improved. A 400nm thick SiO2 is sputtered at the EAM regions to locally create defects in the surface of pin InGaAsP/Imp layer structure. Rapid thermal Annealing (RTA) technique at 850oC is then used to inter-diffuse the atom of quantum wells. A SOA-integrated EAM is fabricated on such template. Ti/Pt/Au and Ni/AuGe/Ni/Au are used for p-type and n-type metallization. An optical waveguide structure is defined by selective undercut-etching active region. The PMGI is spun for planarization and bridging. A Ti/Au is finally deposited as microwave coplanar waveguide. A DC measurement of photocurrent spectrum is performed to examine the wavelength shift. A 10nm shift is found between EAM and SOA regions. Modulation efficiency of 15dB/V with extinction ratio of higher than 20dB is observed in EAM device. And the optical gain of SOA is found as 3dB at 1540nm excitation wavelength. -3dB bandwidth of 20GHz is obtained. In comparison with sample without intermixing, the same results are achieved in intermixing sample, suggesting no regrowth processing is needed for obtaining the same quality of optoelectronic integration.

The three wave mixing process was modeled in GaAs:AlGaAs superlattices using two new modeling tools that were developed in the course of this work: A 2D beam propagation tool for optimizing quasi-phase matching gratings, and a 1D iterative beam propagation tool for determining the output powers and threshold of optical parametric oscillators of arbitrary geometries. The 2D tool predicts close to 80% enhancement of conversion e ciency by phase matching near 800 nm compared to 775 nm, which was the originally designed operation wavelength. The model also predicts resonant behaviour for an abrupt grating pro le. The 1D tool was used to determine the threshold conditions for para- metric oscillation for di erent geometries. The performances of di erent phase matching approaches in AlGaAs were quantitatively compared. The model also indicated the need for pulsed operation to achieve reasonably low threshold powers in AlGaAs waveguides.

The three wave mixing process was modeled in GaAs:AlGaAs superlattices using two new modeling tools that were developed in the course of this work: A 2D beam propagation tool for optimizing quasi-phase matching gratings, and a 1D iterative beam propagation tool for determining the output powers and threshold of optical parametric oscillators of arbitrary geometries. The 2D tool predicts close to 80% enhancement of conversion e ciency by phase matching near 800 nm compared to 775 nm, which was the originally designed operation wavelength. The model also predicts resonant behaviour for an abrupt grating pro le. The 1D tool was used to determine the threshold conditions for para- metric oscillation for di erent geometries. The performances of di erent phase matching approaches in AlGaAs were quantitatively compared. The model also indicated the need for pulsed operation to achieve reasonably low threshold powers in AlGaAs waveguides.

In this work , impurity free vacancy diffusion (IFVD) quantum well intermixing(QWI) technology by high thermal-expansion-induced stress is used to perform bandgap engineering. In this paper, 1530nm InGaAsP multiple QWs sandwiched by p-InP (2£gm thickeneess, top) and n-InP (bottom) material is used as testing material structure also laser fabrication material, where contact materials (InGaAs and InP) on p-InP are used for comparison. By the difference between thermal expansion coefficients of SiO2 on the different material (InGaAs, InP), large different behaviors of QWI are observed, while low different dependence on defects created by ion-implantation is found. Above 70nm photo luminance (PL) wavelength shift of InGaAsP MQW below 2£gm thick InP is realized in this method. Further more, CW in-plane laser structures are also successfully fabricated and demonstrated by such QWI, giving the same shift as PL. It shows that good qualify of material can be obtained in such QWI method. Using local deposition of SiO2 causes different bandgap materials, re-growth free processing for monolithic integration can be expected, offering a powerful scheme of QWI for bandgap engineering.

In this work, a quantum well intermixing(QWI) technology, called impurity free vacancy diffusion(IFVD), is used to do the bandgap engineering in an optoelectronic monolithic integration. The monolithic integration of SOAs and EAMs is taken as an example. By IFVD, the transition energy levels of EAM quantum wells can be shifted to shorter wavelength region, while SOA quantum wells are kept the same. Therefore, the overall SOA-integrated EAM efficiency can be improved. We use dielectric film¡XSiO2 and Si3N4 to control the impurity free vacancy diffusion, both of these two dielectric layer will induce stress on the wafer, but they will come to the totally different result base on the difference atom chemistry with the substrate. Using Ga atom diffusion into SiO2 to relax stress, the IFVD will be operated to enhance quantum well intermixing, leading to energy bang transition change. On the other hand, with Si3N4 film, no significant intermixing is observed, implying atom chemistry dominates the whole process. Also, a super critical fluid technique by H2O2 is also employed to further improving SiO2 quality, a as large as 180nm blue shift is obtained, further improving such mechanism. Through difference properties between SiO2 and Si3N4 dielectric layers, different bandgap transitions in one single chip can be controlled in an area of 30£gm¡Ñ50£gm, leading to a planar bandgap engineering. Use these techniques, an EAM-SOA integration is designed and fabricated, obtaining an wavelength offset of 40nm with good quality of material structure. In the future, we can use this technique on large scale chip, tuning the bandgap to make photonic integration circuit without re-growth.

The main objectives of this thesis are to develop viable process and/or device technologies for bandgap tuning of 1300-nm InGaAs/GaAs quantum-dot (QD) laser structures, and broad linewidth 1300-nm InGaAsP/InP quantum well (QW) superluminescent diode structures. The high performance bandgap-engineered QD laser structures were achieved by employing quantum-dot intermixing (QDI) based on impurity free vacancy diffusion (IFVD) technique for eventual seamless active-passive integration, and bandgap-tuned lasers. QDI using various dielectric-capping materials, such as HfO2, SrTiO3, TiO2, Al2O3 and ZnO, etc, were experimented in which the resultant emission wavelength can be blueshifted to ∼ 1100 nm ─ 1200 nm range depending on process conditions. The significant results extracted from the PL characterization were used to perform an extensive laser characterization. The InAs/GaAs quantum-dot lasers with QDs transition energies were blueshifted by ~185 nm, and lasing around ~1070 – 1190 nm was achieved. Furthermore, from the spectral analysis, a simultaneous five-state lasing in the InAs/InGaAs intermixed QD laser was experimentally demonstrated for the first time in the very important wavelength range from 1030 to 1125 nm. The QDI methodology enabled the facile formation of a plethora of devices with various emission wavelengths suitable for a wide range of applications in the infrared. In addition, the wavelength range achieved is also applicable for coherent light generation in the green – yellow – orange visible wavelength band via frequency doubling, which is a cost-effective way of producing compact devices for pico-projectors, semiconductor laser based solid state lighting, etc. [1, 2] In QW-based superluminescent diode, the problem statement lies on achieving a flat-top and ultra-wide emission bandwidth. The approach was to design an inhomogeneous active region with a comparable simultaneous emission from different transition states in the QW stacks, in conjunction with anti-reflection coating and tilted ridge-waveguide device configuration. In this regard, we achieved 125 nm linewidth from InGaAsP/InP multiple quantum well (MQW) superluminescent diode with a total output power in excess of 70 mW with an average power spectral density of 0.56 mW/nm, and a spectral ripple of ≤1.2 ± 0.5 dB. The high power and broadband SLD with flat-top emission spectrum is a desirable as optical source for noninvasive biomedical imaging techniques employing low coherence interferometry, for instance, optical coherence tomography (OCT).