A Technique for Trap Determinations in Low-Resistivity Semiconductors

Abstract

A simple method is described to allow the use of thermally stimulated conductivity (TSC) measurements for low-resistivity semiconductors. A p-n junction or Schottky barrier is formed to provide the required high-resistivity region. Trap populations can be inverted either by light or by changes in diode bias, but different traps may be seen in each case. The accuracy of trap concentration determinations is improved over ordinary TSC measurements since the gain is close to unity, and the active volume can be accurately found from capacitance measurements. The use of the method is demonstrated by the measurement of trap energies and densities in a sample of GaAs0.5P0.5 alloy with an electron concentration of about 1015 cm−3. Two main traps were seen, one at 0.20 eV from the conduction band and the other at 0.41 eV from the valence band, with concentrations of, respectively, 1×1014 cm−3 and 5×1014 cm−3. The method has also been successfully applied to silicon.