Abstract
Carrier freezeout and impurity conduction in lightly doped p-type GaAs have been studied in two groups of -type GaAs–undoped As–-type GaAs capacitors. For one group the substrate doping was ∼5× ; for the other ∼5× . From the temperature dependence of the appearance of a Gray-Brown dip in the capacitance-voltage curves at fixed frequency and temperature, the separation of the Be acceptor from the valence band, , is ∼20 meV for both groups. The activation energy for ac transport in -type GaAs, , is determined from admittance measurements at fixed bias and variable temperature and frequency. For the lighter-doped samples, =17–23 meV, which is consistent with the value of . For the heavier-doped samples, ∼6 meV; ac transport is either through a well-defined impurity band separated by ∼6 meV from the energy level of an isolated acceptor, or by activated hopping.
- Received 28 June 1991
DOI:https://doi.org/10.1103/PhysRevB.44.13487
©1991 American Physical Society