Electrical Properties of Si-Doped Al_xGa_1-xAs Layers Grown by MBE

Abstract

Electrical properties of Si-doped Al x Ga 1- x As layers grown by MBE were investigated as a function of AlAs mole fraction (0≦ x ≦0.5). Although ionization energy of Si donor remained constant at a few meV in the range of 0≦ x ≦0.25, it rapidly became larger with increasing x for x ≧0.25. It was found to be 60 meV for x =0.3, which is the composition used in HEMT. The overall trend was similar to the case of Sn- or Te-doped Al x Ga 1- x As layers. However, the ionization energy was found to be independent of doping concentration, unlike the case of Sn-doped Al x Ga 1- x As layers grown by MBE.