The main work of this thesis is to design the TE-polarized SOA structures for booster amplifier, and the polarization-independent SOA structures for preamplifier at receiver end. In the SOA structure, we add a lattice-matched ternary compound InGaAs as an extra quantum well in separate-confinement heterostructure (SCH) layer. The purpose is to result in the band-filling/shrinkage and lead to change the absorption coefficient. Therefore, the refractive index change will be increased, and the structure can work as a Mach-Zehnder interferometer under reverse bias. We also added an electron barrier InAlAs layer to reduce the carriers accumulation in the extra InGaAs QW. After the epitaxy of MOCVD, this designed structure was processed to be a ridge laser. From the measurements of ridge laser, the barrier InAlAs could not efficiently stop the carrier injection into the extra InGaAs QW. The other part of this thesis is to set up a digital signal apparatus to analyze the RHEED pattern on the screen of the chamber. We make a connection between CCD camera and PC utilizing the framegrabber in RHEED system, and develop the programs from LabVIEW and IMAQ to obtain the functions we need. Further, from the tests of grabing and analysis for RHEED pattern, the digital signal system on RHEED pattern has been successfully demonstrated.

The thesis consists of two aspects: (1) Research on regrowth by molecular beam epitaxy, and (2) Silicon monoxide coating. In part one, we used (NH4)2Sx to passivate the InAlGaAs/InP surface. From the X-ray photoelectron spectroscopy (XPS), the passivated surface shows a dramatic reduce of oxidation. A preparation chamber for the regrowth has been setup to proceed the sulfur passivation method. We can obtain a clean surface for regrowth after heating and putting samples in the high vacuum chamber. In the design of regrowth layers, we have found the best waveguide structure by regrowth. When the ridge width is 2.5 mm with etching depth 1.4 mm, a circular mode profile can be obtained by Fimmwave simulation. In the integration between devices, we have designed the best waveguide structure after regrowth by BeamProp 3D. The best design will make the propagation loss smaller than 0.21%. The second part is anti-reflection (AR) coating by silicon monoxide (SiO) deposition. The SiO refractive index of 1.8837 was obtained by transmission, and ellipsometer measurements. The corresponding AR coating thickness for InP substrate is 2057 &#x00C5;. In order to make AR coating on lasers of different effective index, we design the double-layer coating. For Beam Expander Semiconductor Optical Amplifier (BESOA), SiO2 / SiO and Si3NX / SiO double-layer coatings were compared with SiO single layer. The reflectance (R) was reduced 16.86 % and 25.12 %, respectively, and the R < 1% bandwidth extends 200 &#x00C5;.

Gamma-phase lithium aluminate (LiAlO2) single crystal is grown by Czochralski pulling method and a-plane LiAlO2(LAO) is chosen as the substrate for subsequent gallium nitride (GaN) epitaxial growth by plasma-assisted molecular beam epitaxy (PAMBE). The lattice mismatch between the nitride and the substrate is greatly reduced due to small lattice mismatch of~0.3% between [0001]GaN and [010]LAO and of~1.7% between [11-20]GaN and [001]LAO in the plane of the substrate LAO(100). Pure hexagonal [10-10]GaN is successfully grown directly on the LAO substrate without buffer layer. Crystal quality and properties are analyzed through a series of measurements, including reflection high-energy electron diffraction (RHEED), field-emission electron microscopy (FESEM), electron backscatter diffraction (EBSD), x-ray diffraction and cathodo luminescence (CL).

This work is to control the fluxes of the Ga, In and Al sources in our MBE system to grow lattice-matched InGaAs, InAlAs and InGaAlAs epi-layers on InP substrates. With the As overpressure condition in the MBE system, we can control the temperature of Ga K-cell to modulate the flux of Ga. In ideal situation, the flux of Ga has a direct ratio with the GaAs growth rate on GaAs substrate, so we can find the Ga flux dependence on temperature by measuring the RHEED oscillation frequency. From the growth rate data of InGaAs on GaAs substrate at lower In composition, the In flux was obtained by comparing the growth rate ratio to the GaAs case. In the same way, we can also get the flux of Al by the growth of AlAs or AlGaAs on GaAs substrate. With the results of flux experiment, we can modulate the temperature of Ga, In and Al K-cells to compose InGaAs, InAlAs and InGaAlAs lattice-matched on InP substrates. The epi-layer quality was examined by X-ray diffraction and photo-absorption spectrum. We have built the flux equations for the Ga, In and Al sources from the experiment data. With the In K-cell temperature at 833~836¢J, Ga(1) at 931¢J and Al at 1094¢J, we have grown ternary compound semiconductors of In0.532Ga0.468As and In0.523Al0.477As lattice-matched on InP substrates. When the In K-cell temperature at 833~836¢J, Ga(2) at 912¢J and Al at 1059¢J, a quaternary compound semiconductor of In0.527Ga0.245Al0.228As (Eg=1eV) lattice-matched on InP substrate was demonstrated.

Abract This paper concems studies of CIS solar cell based on ZnSe an ZnSeTe window layer. ZnSe an ZnSeTe films are grown by Molecular Beam Deposition (MBD).This research is important for several reasons : (1)Development of non-cadmium buffer layer may be essential for CIS solar cells to be accepted in the marketplace ; (2)Development of direct ZnO/CIS cells could lead to a simplified cell (3)knowledge gained in investigations of ZnO and ZnSeTe buffer layer may help us understand the unique role CdS plays in CdS/CIS solar cell .

The work of this thesis includes the growth of TE polarization and polarization insensitive semiconductor optical amplifier structures by molecular beam epitaxy. The former is suited to fabricate the SOA and laser of the emitter, the latter is suited to fabricate the SOA of the repeater and receiver. The materials of InAl(1)As, InGa(1)Al(2)As and InGa(2)As were used to be the cladding layer, SCH layer and quantum well(QW), respectively. The first kind of our SOA structures is for 1.55-£gm TE polarization. The materials of InGa(1)As and InGa(2)As were used to be QW and sub-well, respectively. The second kind of our SOA structures is for 1.55-£gm polarization insensitive. To get polarization insensitive characteristics we use tensile strained InGa(3)As material and add two very thin compressive strain layers, InGa(1)As, in QWs to be sub-wells to mostly confine hh1 state. It has the effect of reducing red shift on the e1-hh1 transition and help to partially balance the strain in QW before the thickness of the tensile strained InGa(3)As exceeds one half of the critical layer thickness. These two kinds of structures include three QWs with modulation doping. It can reduce transparency current and noise figure and increase the saturation output power of SOA with the n-type modulation doping. We had successfully grown the polarization insensitive SOA structure for 1.52-£gm. The wavelength of TE polarization SOA structures we grew were at 1.45(&#x00B5;m) and 1.47(&#x00B5;m) and there were somewhat differences between the designed and grown. We can increase the PL efficiency after rapid thermal annealing at 550¢J for 30(s)~45(s).

The work of this thesis includes designs, molecular beam epitaxy (MBE) growths and optical study of electro-absorption modulator (EAM) structures. Three EAM structures are designed near 1.5 um : symmetric, asymmetric multiple quantum wells (MQWs) of TE polarization, and polarization insensitive MQWs. For symmetric and asymmetric MQWs simulation of TE polarization, their red-shift are 31 nm and 50 nm, respectively, as the electric field decrease from -40 kV/cm to -120 kV/cm. For polarization insensitive MQWs, we use the strained quantum-well concept to achieve same transition energy and absorption. After growth by MBE system, the samples were fabricated in mesa type by photolithography and wet etching. For symmetric and asymmetric quantum wells of TE polarization¡Gthe red-shift are 16 nm and 49 nm, respectively, as the bias decrease form 0-1 volt to 0-6 volt. Because of small ¡µn near subband transition energy, these two samples exhibit small chirp parameter. However, the photoluminescence (PL) and photocurrent spectra of these two ones were not near 1.5 um and obvious absorption edge. The possible reason is that the molecular beam flux have changed during growth. For polarization insensitive MQWs, the PL spectra shows 1494 nm, which only 25.6 nm differ from our design. Also, the photocurrent spectra of TE and TM polarization nearly exhibit same transition energy and have small chirp parameter.

Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xvii, 161 p. : ill. Includes abstract. Includes bibliographical references (p. 154-161).

Thesis (Ph. D.)--School of Electrical and Computer Engineering, Georgia Institute of Technology, 2004. Directed by Gary S. May. / Includes bibliographical references (leaves 109-113).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 44-48). Also available in electronic version. Access restricted to campus users.