Production of Midgap Electron Traps by Ga Out-Diffusion in Rapid-Thermal-Processed GaAs with Sio2 Encapsulants

Abstract

ABSTRACTProduction of midgap electron traps in rapid-thermal-processed (RTP) GaAs with sio2 encapsulant has been studied by deep-level transient spec-troscopy in connection with the rapid out-diffusion of Ga through Sio2. Sio2 films of 50 and 1250 nm in thickness have been deposited on LEC n-type (100) GaAs doped with Si. RTP has been performed at 760 and 910°C for 9 s. The broadened DLTS signal consists of four electron traps with the energy levels of Ec - 0.79, 0.83, 0.78 and 0.81 eV. The depth profiles of the total concentration of four traps coincide with those of the decreased carrier concentration multiplied by 0.14 and 0.054 with RTP at 910 and 760°C for 50-nm-thick samples, respectively. These are 0.29 and 0.026 for 1250-nm-thick samples. This means that the origin of these traps is the Ga vacancy formed by the out-diffusion of Ga since the decrease of the carrier concentration by RTP has been ascribed to the formation of VGa-SiGa complex. However, the observation of the persistent photocapacitance quenching effect indicates that these traps are correlated with the As antisite formed by the migration of As into the Ga vacancy. Four kinds of complex defects including the As antisite are produced by RTP which are complex defects of EL2 group.