Donor Levels in Si-Doped AlGaAs Grown by MBE

Donor levels of MBE-grown Si-doped Al x Ga 1- 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.