GaAs surface passivation for device applications

Abstract : Three new MBE grown samples of graded Al(1-x)Ga(x)As on GaAs (100) have been prepared and characterized in an effort to develop a practical dielectric for GaAs surface passivation. In addition a systematic C-V study of a previously grown MBE structure as a function of oxidation time was carried out. In all cases, the thermal oxide produced on these samples appears to have excessive leakage which may be the cause for the absence of any observed inversion. An analysis of previously published results on thermally oxidized MBE grown graded layers of Al(1-x)Ga(x)As on GaAs suggests that these results may not be completely understood. Current results suggest that other insulators should be investigated as possible substitutes for the thermally grown oxides. Several device structures involving deposited SiO(x) on GaAs (100) surfaces of known composition did not produce satisfactory C-V results from a passivation criteria. A novel photochemical process was developed to deposit nearly stoichiometric SiO2 on GaAs surfaces at room temperature. Several methods of depositing Al oxides were investigated; Al deposition in the presence of an O2 plasma discharge was found to produce relatively thick layers of an intermediate Al oxide. (Author)