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Schottky characteristics of undoped AlInAs grown by metal-organic chemical-vapor deposition have been investigated. I-V characteristics and their dependence on donor concentrations in AlInAs layers were explained well by assuming the existence of an interfacial layer. The presence of oxygen atoms at the metal-AlInAs interface was revealed by Auger electron spectroscopy measurements. The oxide formation on AlInAs surface may be an inevitable result because of the high composition of aluminum atoms in AlInAs. Reduction in donor concentration in AlInAs layers is effective in minimizing the influence of the interfacial layer on barrier height lowering. Reduction in gate leakage current was successfully demonstrated for fabricated GaInAs/AlInAs high-electron-mobility transistors by reducing donor concentration in AlInAs Schottky layers.

Base metallization stability in InP/InGaAs heterojunction bipolar transistors and its influence on leakage currents

Donor levels of MBE-grown Si-doped Al x Ga1-x As have been characterized by a combination of the C-V method and capacitance and current transient spectroscopy. Although most electrons are supplied by so-called DX centers in the AlAs mole fraction (x) range of 0.3∼0.7 in this material, it is found that a small amount of shallow donors are still present. The concentrations of the DX center and the shallow donor are determined in detail as a function of AlAs mole fraction and Si doping level. The activation energy obtained by the Hall effect measurement is discussed in association with these data.