Stable, low resistance ohmic contacts to p-type GaAs were studied for use in semiconductor laser applications. Comparison was made between Cr/Au, Au:Be and Pd/Au:Be metallizations. Regions of P+ were formed in N-type GaAs by a spin-on source which was rapid diffused at 950°C for 6s. Surface doping of 2×1020/cm3 and junction depth of 0.4 μm were determined by SIMS, groove and stain, and electrochemical profile. Metallizations were accomplished by thermal evaporation with a base pressure of 3×10-6 Torr. Sintering of the metallizations was done by furnace or RTA at 350°C. This sintering temperature was selected after RBS studies predicted an absence of significant interdiffusion. Pd/Au:Be yielded the best result of 0.3 μΩ-cm2 based upon transmission line, cross-bridge Kelvin and van der Pauw studies. A layer of BeO was revealed on the surface of Au:Be contacts by Auger studies. Cross-section TEM studies on Pd/Au:Be revealed a uniform layer of alloyed Ga-Au with an absence of spiking.

A method for wafer annealing which is effective in suppressing defects and raising minority carrier diffusion lengths in n-type bulk GaAs is described. The beneficial effect of the annealing is shown to be associated with the proximity surface with measurements of photoresponse as a function of depth. The concentration of the hole trap HCX (Ev+0.29eV) varies as a function of depth from the surface, qualitatively, as might be expected of the concentration of the dominant recombination center in the material. The impact of improving the material in this manner on the performance of Zn diffused solar cells is demonstrated.

Carbon in LEC GaAs was found to be introduced as CO from the ambient atmosphere; the oxygen concentration in the crystals decreased with increase in the duration of melting. An equilibrium segregation coefficient of oxygen in GaAs crystals was found by charged particle activation analysis to be 0.1, the value of which was smaller by a factor of 3~4 than that reported before.

The Kyropoulos growth technique has been combined with in-situ synthesis to yield high purity undoped crystals of 300 to 700 gm charges of InP. Etched wafers show a uniform dislocation density across 70mm diameter in contrast with the "W" pattern created by LEC. Use of an axial magnetic field in Kyropoulos growth reduces the dislocation density by an order of magnitude, to 1 × 104cm-2. By combining Kyropoulos growth with in-situ synthesis of the indium phosphide, high mobility (4.6×104 at 77 C) undoped single crystals have been obtained.

Current-voltage characteristics of Au contacts formed on buried implanted oxide silicon-on-insulator structures and molecular beam epitaxially grown GaAs on (1012) sapphire and silicon-on-sapphire substrates indicate that the dominant transport mechanism in these films is space-charge-limited current conduction in the presence of deep-level states. The deep-level parameters, determined using an analysis of the current-voltage characteristics, appear to be sensitive to the nature of crystallographic defects present in the grown layers. Conduction in the GaAs film on SOS was dominated by one discrete state located ~ 0.28eV below the conduction band-edge, which is close to the El center uniquely observed in the molecular beam epitaxially grown GaAs-on-Si. Discrete levels are also observed in annealed buried implanted oxide silicon-on-insulator films. In contrast, the GaAs films deposited directly on (1012) sapphire substrates and rapid-thermally annealed high-dose As implanted buried oxide SOI films appear to have a continuous distribution of states. The distributed states in GaAs films deposited directly on sapphire probably arise from the electrical activity of the double-position boundaries present in this material system.

Surface structure of (NH4)2S treated GaAs. is investigated using PL (PhotoLuminescence), XPS (X-ray Photoelectron Spectroscopy) and RHEED (Reflection of High Energy Electron beam Diffraction). The data taken with these techniques show the strong dependence upon the crystal orientations coming from the stabilities of chemical bonds of Ga-S and As-S on GaAs crystals. The greater enhancement of PL intensity, the clearer RHEED patterns and the smaller amount of oxides on (111)A than (111)B implies the realization of a more stable structure composed mainly of the Ga-S chemical bond.

In this work we have studied the effects of silicon planar doping on the electrical and optical properties of GaAs, and the effects of rapid thermal annealing on AIGaAs planar-doped structures. MBE-grown GaAs epilayers with multiple planar-doped layers displayed a 1.2 eV photoluminescence peak, presumably due to gallium vacancy - donor complexes, for samples with nominal silicon sheet densities much greater than measured charge densities. The Hall mobilities of these samples were also reduced compared to both uniformly-doped and planar-doped structures whose silicon areal densities were more nearly equal to measured sheet charge densities, although X-Ray rocking curves were nearly identical in all cases. Planar-doped AIGaAs Schottky diodes had nearly ideal electrical characteristics. Rapid thermal annealing of the planar-doped structures before fabrication increased the diode ideality factor from n=1.06 to n=1.60, seriously degraded the saturation current and breakdown voltage, and increased the doping profile FWHM from 60Å to 170Å.

We have studied the effects of chemical etching in potassium iodide(KI) aqueous solution, vacuum exposure and bulk heating on the photoluminescence(PL) spectra of mercuric i0dide(HgI2). Different contact materials deposited onto HgI2 were also investigated, such as Pd, Cu, Al, Ni, Sn, In, Ag and Ta. These processing steps and the choice of a suitable electrode material are very important in the manufacturing of high-quality mercuric iodide nuclear detectors. Comparisons are made between the front surface photoluminescence and transmission photoluminescence spectra.

The technique of Synchrotron White Beam topographic imaging in grazing Bragg-Laue geometries has been developed at the Stony Brook synchrotron topography station at the NSLS. This technique enables imaging of defects in subsurface regions of thickness which can range from hundreds of Angstroms to hundreds of microns as determined by the penetration depth of the X-rays. This penetration depth, which is shown to be determined by the kinematical theory of X-ray diffraction, can be conveniently varied, in a controlled manner, by simple manipulation of the diffraction geometry, thereby enabling a depth profiling of the defect content.

The fundamentals of the technique are described, and its advantages and disadvantages compared to existing techniques are discussed in detail. Examples of application of the technique in the characterization of defects in thin epitaxial films of GaAs on Si, are given, and the general applicability of the technique is discussed.