Capacitance Measurements on Au–GaAs Schottky Barriers

Abstract

Dark capacitance measurements have been made on Au–GaAs Schottky barriers using boat‐grown, oxygen‐doped n‐type GaAs with room‐temperature carrier concentrations from 2×10¹³ to 4×10¹⁶ cm⁻³. The voltage and time dependence of the capacitance was analyzed using a modified version of Goodman's model for traps in depletion layers. The results yield a concentration of the dominant active trap of 1–4×10¹⁶ cm⁻³ in all the crystals examined. From the variation in the time dependence of the capacitance in the range 275°–365°K, the energy for the emission of an electron from this trap is 0.90±0.02 eV. Other aspects of the capacitance data locate this trap at around 0.7 eV below the conduction band, which is the energy previously assigned. Another, faster time‐dependence observed in the higher‐resistivity material was investigated in the range 225°–255°K. The activation energy associated with the latter time dependence is found to be 0.7 eV. The behavior of the capacitance at high reverse bias is explained in terms of electron capture by the dominant trap as the current increases due to impact ionization.