Electrolyte electroreflectance (EER) experiments were performed on In0.22Ga0.78As/GaAs single quantum wells grown by the conventional molecular-beam-epitaxy (MBE) shutter operation, and also by modified MBE shutter operation intended to form more compositionally abrupt normal and inverted interfaces. The latter included controlled thermal desorption of the surface segregated In at the InGaAs layer surface (flash off), and the deposition of In at the InGaAs/GaAs interface to eliminate compositional broadening (predeposition). The fundamental energy gap and subband transitions were determined experimentally, and compared with an accurate calculation of the potential well problem including strain. These results confirmed the segregation of In atoms near the interface. The segregation was maximum in the conventional (normal) MBE sample and least with the modified growth incorporating predeposition and flash off, as expected. The segregated atoms are observed to act as dopants and form junctions near the InGaAs/GaAs interface. This study shows that EER can be used as an effective tool for studying the segregation process in MBE growth.

Resonant cavities are used to enhance the absorption efficiency in p-type GaAs/AlGaAs quantum-well infrared photodetectors. The cavities are fabricated by applying thick gold films on the detector bottom sides after substrate removal via selective wet etching. The observed peak enhancement and spectral shape are in good agreement with model predictions. Peak absorption of about 25% is obtained for the device studied.

Electron beam source molecularbeam epitaxy of III-V compoundsSurface composition is known to influence cation and anion incorporation rates during III-V molecular-beam epitaxy (MBE), [See, for example, Van Hove and Cohen, Appl. Phys, Lett 47, 726 (1985),] Thus, incorporation rates are expected to vary at heterointerfaces, The details of how incorporation rates vary in time during heterointerface formation are of interest because they completely determine resulting compositional profiles andlor layer thicknesses, In this study desorption mass spectrometry is used to determine the time dependence of incorporation rates during MBE growth of IU-V heterostructures, with an emphasis on the heterointerface formation process, Under many conditions incorporation rates are found to vary in a nonsteplike manner, resulting in nonsteplike compositional profiles, Three different heterointerfaces are investigated: AIGaAs on GaAs, GalnAs on GaAs, and GaAsSb on GaAs, At growth temperatures for which significant Ga desorption occurs, AIGaAs on GaAs interfaces are found to be enriched in Al content relative to adjacent AIGaAs, In addition, transients are observed in the Ga desorption rate which suggest the occurrence of an Al-Ga displacement reaction, When Sb desorption is significant, GaAsSb on GaAs interfaces are found to be enriched in Sb content relative to adjacent GaAsSb, And when In desorption is significant, GalnAs on GaAs interfaces are found to be enriched in In content relative to adjacent GalnAs, The latter result is verified by x-ray and photoluminescence measurements on separately grown, narrow, single GaInAs/GaAs quantum wells, Compositional grading for each system investigated is found to occur over a distance of about two to four monolayers, These results are shown to be consisteut with a model which assumes simple first order desorption behavior and which incorporates strain-dependent activation energies for desorption,

The electrical properties of Ge-implanted GaAs have been studied. Room-temperature implantation was performed at 120 keY with doses ranging from 5X 10 12 to 3X 10 15 /cm 2 . Implanted samples were annealed with pyrolytic Si3N4 encapsulants at temperatures ranging from 700 to 950°C. It was found that both pand n -type layers were produced, depending upon ion dose and anneal temperature. For doses of -1