INVESTIGATION OF HETEROJUNCTIONS FOR MIS DEVICES WITH OXYGEN-DOPED ALXGA1-XAS ON N-TYPE GAAS

Metal-insulator-semiconductor (MIS) structures were prepared with high-resistivity oxygen-doped Al0.5Ga0.5As layers on n-type GaAs. These layers were grown by molecular-beam epitaxy (MBE). Capacitance-voltage measurements of MIS structures on both conducting and high-resistivity substrates demonstrate the achievement of deep depletion for reverse-bias and a near-flatband condition at zero bias. Measurement of the output characteristics of a majority-carrier depletion mode MISFET illustrates the application of this MIS technique to three terminal devices. The presence of a 2000-Å-thick O-doped Al0.5Ga0.5As layer on n-type GaAs was found to enhance the photoluminescent intensity of the n-GaAs layer by 52 times over that of an exposed GaAs surface. The measurements described here demonstrate that the use of single-crystal lattice-matched heterojunctions of O-Al0.5Ga0.5As-n (GaAs) avoids large interface state densities. Admittance spectroscopy measurements permitted assignment of the dominant deep level in O-doped Al0.5Ga0.5As as 0.64±0.04 eV.