Electron traps in GaAs0.6P0.4 p+n diodes fabricated by Zn implantation and rapid thermal annealing

Abstract

Majority-carrier traps in p+n diodes fabricated by rapid thermal annealing (RTA) of Zn-implanted GaAs0.6P0.4:Te and in Schottky diodes fabricated on GaAs0.6P0.4:Te after only RTA were studied using deep-level transient spectroscopy (DLTS). RTA using halogen lamps was performed in the temperature range 830–1000 °C for approximately 6 s without any encapsulant. Two electron traps E1 and E2 were observed for both p+n and Schottky diodes and were found to have thermal emission activation energies of 0.20 and 0.36 eV, respectively. The broadened DLTS spectrum was observed and reproduced using the Gaussian distribution for thermal emission activation energies of these traps. Furthermore, traps E1 and E2 have thermal activation energies of 0.09 and 0.24 eV for electron capture, respectively. It is considered that these traps are native defects and may belong to donor-related (DX) centers. Depth profiles of shallow donors and traps were determined using capacitance-voltage measurements because of anomalously high concentrations of these traps. Shallow donor and trap concentrations were found to decrease over several μm from the surface for RTA Schottky diodes above ∼900 °C, but were observed to be uniform for RTA p+n diodes. The concentrations calculated for shallow donors and trap E2 by RTA at 1000 °C decreased exponentially with depth. The difference between p+n and Schottky diodes, and the possible mechanism for the decrease of shallow donor and trap concentrations by RTA are discussed. It is possible that the decrease of shallow donor and trap concentrations by RTA is due either to their interaction with vacancies produced near the surface or to their out-diffusion.