Investigation of heterojunctions for MIS devices with oxygen-doped AlxGa1−xAs on n-type GaAs

Abstract

Metal‐insulator‐semiconductor (MIS) structures were prepared with high‐resistivity oxygen‐doped Al_0.5Ga_0.5As 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 Al_0.5Ga_0.5As 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‐Al_0.5Ga_0.5As–n (GaAs) avoids large interface state densities. Admittance spectroscopy measurements permitted assignment of the dominant deep level in O‐doped Al_0.5Ga_0.5As as 0.64±0.04 eV.