Deep Electron Traps In Mbe Gaas On Si

Abstract

ABSTRACTDeep electron traps were investigated in MBE GaAs grown directly on Si substrates with orientations a few degrees off the <100> axis. Capacitance Deep Level Transient Spectroscopy (CDLTS) revealed the presence of eleven electron traps in the GaAs epilayer. Their activation energies ranged from 0.21 eV to 0.83 eV below the conduction band. Most of these traps were previously observed in homoepitaxial GaAs films grown under As-rich conditions (VPE, MBE), or in electron irradiated bulk GaAs. Trap concentrations tracked Si dopant density and MBE growth conditions. Observed deep levels are not introduced by metals or other contaminants present at the GaAs-Si interfaces. Rather, they are caused by defect complexes. These complexes involve native point defects, whose formation is favoured by As-rich environments, by lattice mismatch, and by different thermal expansion coefficients. Si dopant atoms may also participate in the formation of these defects. A similar deep level generation mechanism is proposed for the electron traps in homoepitaxial MBE GaAs layers.