Electrical characterization of p-GaAs epilayers disordered by doped spin-on-glass

Abstract

Impurity-free disordering (IFD) of uniformly doped p-GaAs epitaxial layers was achieved using either undoped or doped (Ga or P) spin-on-glass (SOG) in conjunction with rapid thermal annealing in the temperature range from 800to925°C. Capacitance-voltage measurements showed a pronounced increase in the doping concentration (NA) in the near-surface region of the layers disordered using both undoped and P:SOG. The increase in NA showed an Arrhenius-like dependence on the inverse of annealing temperature. On the other hand, NA did not change significantly for Ga-doped SOG. These changes can be explained by the relative injection of excess gallium vacancies (VGa) during IFD of p-GaAs by the different SOG layers. Deep-level transient spectroscopy showed a corresponding increase in the concentration of a defect HA (EV+0.39eV), which can be attributed to Cu, in the undoped and P:SOG disordered p-GaAs layers, but not in the epilayers disordered by Ga:SOG. We have explained the increase in free carrier concentration by the segregation of Zn atoms towards the surface during the injection of VGa. The redistribution of Zn during disordering of buried marker layers in GaAs and Al0.6Ga0.4As using either undoped or Ga-doped SOG was verified by secondary-ion mass spectrometry.