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

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 800 to 925 °C. Capacitance-voltage measurements showed a pronounced increase in the doping concentration (N _A) in the near-surface region of the layers disordered using both undoped and P:SOG. The increase in N _A showed an Arrhenius-like dependence on the inverse of annealing temperature. On the other hand, N _A did not change significantly for Ga-doped SOG. These changes can be explained by the relative injection of excess gallium vacancies (V _Ga) 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 (E _v+0.39 _eV), 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 V _Ga. The redistribution of Zn during disordering of buried marker layers in GaAs and Al _0.6Ga _0.4As using either undoped or Ga-doped SOG was verified by secondary-ion mass spectrometry.