Energy and Depth Distributions of Interface States and bulk Traps and their Electronic Effects in GalnAs/GaAs Heterojuntions

Abstract

ABSTRACTWe have studied the lattice-mismatch-induced defects both at the interface and in the bulk (GaAs buffer layer ) of Ga0.92In0.08As/GaAs heterojunctions by means of C-V characteristics and constant capacitance deep level transient spectroscopy (CC-DLTS). The Ga0.92In0.08As (n+)/GaAs (P) samples, with the thickness of GalnAs layer at 0.1μm, 0.25μm, 0.5μm, and 1.0μm, were grown by MBE. The depth profiles of bulk hole traps in the GaAs buffer layer were measured by the DLTS technique as a function of the in-plane lattice mismatch. The concentration of lattice-mismatch-induced traps decreased exponentially with distance away from the interface. The depth distributions of the mismatch-induced bulk traps appeared to be affected by the pre-existing bulk traps and the dopant impurities in the GaAs buffer layer. Energy distribution of the interface states was obtained by the CC-DLTS and C-V measurements independently. All heterojunctions showed a minimum in the interface state density at about EV+0.83eV. The U-shaped energy distribution with donor- and acceptor-like states is interpreted by the disorder-induced-gap-states model.