Electronic profile of n-InAs on semi-insulating GaAs

The electron density and mobility of VPE-grown 15-μm n-type indium arsenide epilayers have been determined as a function of distance from the gallium arsenide substrate. Both epilayer surfaces show significant increases in density and decreases in mobility from the bulk values (1015–1016 cm−3 and 105 cm2/V sec at 77 °K). The interfacial, or back, surface is apparently dominated by defects to a depth of about 3 μm. The density and mobility profiles are roughly exponential; integrated values are 1.6×1013 cm−2 and 2×103 cm2/V sec. The front surface, highly dependent on applied gate bias, has a density range in accumulation from zero to 5×1012 cm−2 and mobility from 2.5×104 to 3×103 cm2/V sec. The parameters for both surfaces are essentially temperature independent below 80 °K. The front-surface effective mass increases with electron density from its band-edge value of 0.0215me to nearly 0.06 me.