ELECTROREFLECTANCE STUDY OF EFFECTS OF INDIUM SEGREGATION IN MOLECULAR-BEAM-EPITAXY-GROWN INGAAS GAAS/

Electrolyte electroreflectance (EER) experiments were performed on In0 .22Ga0.78As/GaAs single quantum wells grown by the conventional molecu lar-beam-epitaxy (MBE) shutter operation, and also by modified MBE shu tter operation intended to form more compositionally abrupt normal and inverted interfaces. The latter included controlled thermal desorptio n of the surface segregated In at the InGaAs layer surface (flash off) , and the deposition of In at the InGaAs/GaAs interface to eliminate c ompositional broadening (predeposition). The fundamental energy gap an d subband transitions were determined experimentally, and compared wit h an accurate calculation of the potential well problem including stra in. These results confirmed the segregation of In atoms near the inter face. The segregation was maximum in the conventional (normal) MBE sam ple and least with the modified growth incorporating predeposition and flash off, as expected. The segregated atoms are observed to act as d opants and form junctions near the InGaAs/GaAs interface. This study s hows that EER can be used as an effective tool for studying the segreg ation process in MBE growth. (C) 1997 American Institute of Physics.