CROSS-SECTIONAL SCANNING-TUNNELING-MICROSCOPY OF DOPED AND UNDOPED ALGAAS GAAS HETEROSTRUCTURES/

Scanning tunneling microscopy (STM) was used to study the (NH4)(2)S-pa ssivated (110) cross-sectional surfaces of both doped and undoped Al0. 3Ga0.7As/GaAs heterostructures on n(+)-substrates. The ex situ (NH4)(2 )S treatment of the cross-sectional surfaces of heterostructures was f ound to be very stable against oxidation. STM images showed no appreci able deterioration of surface quality in vacuum after more than 40 day s. The spectroscopic results on the undoped epilayer showed diodelike behavior, confirming that an undoped large band gap region can be imag ed by STM through carrier injection from the conductive regions.