Abstract
Freshly grown GaAs epi-layers were passivated with in situ electron beam evaporated nano-thick Y2O3 films in ultrahigh vacuum condition, followed by in situ deposition of a Al2O3 capped layer. The formation of hydroxides in the films and arsenic oxide at Y2O3/GaAs interface after exposed to air will be reported. In the Al2O3/Y2O3/GaAs hetero-structure, neither hydroxides, nor arsenic oxides, were found in the sample; even it was exposed to air and dipped in DI water for 10 min. Moreover, the hetero-structure exhibits well-behaved inversion and accumulation characteristics in capacitance-voltage curves.However, Y2O3 in amorphous and crystalline phase deposited on GaAs at room and elevated temperatures capped with Al2O3 exhibit significant different electrical properties. Let the dielectric constant of Al2O3 be assumed about 8, then the dielectric constants of a-Y2O3 (1.8 nm) and c-Y2O3 (2.5 nm) are estimated to about 3.7-4.6 and 8.6-11.1, respectively. It is suggested that the different growth temperature results in different chemical reactions of Y2O3 with GaAs, thus affecting the electrical properties. XPS will be used to study the chemical reactions of Y2O3 on GaAs at different temperature.