Effect of Cr Concentration on Electrical Properties of Cr-Doped Semi-Insulating GaAs Substrates

Abstract
The chromium concentration in semi-insulating GaAs substrates and its distribution along Cr-doped ingots have been measured by flameless atomic absorption spectrophotometry. When the Cr concentration is lower than a certain value, the Cr distribution can be approximated by the normal freeze equation. Whereas at higher Cr concentrations, the measured distribution deviates from the equation probably due to Cr precipitation. The Cr concentration is found to be closely correlated with leakage currents in the substrates and with activation efficiencies of 28Si ions implanted directly into the substrate.