The electrical characterization of semi-insulating GaAs: A correlation with mass-spectrographic analysis

Abstract

The room‐temperature electrical properties of 28 semi‐insulating GaAs crystals have been determined by using a mixed‐conductivity analysis. It is shown that for most of these samples, such an analysis gives good accuracy for the electron mobility μ_n and electron concentration n, but poorer accuracy for the hole mobility μ_p, hole concentration p, and intrinsic concentration n_i. The intrinsic concentration is determined at 296 °K to be n_i? (1.7±0.4) ×10⁶ cm⁻³, which compares favorably with the theoretical value deduced from the band gap and the effective masses. From a Fermi‐level analysis, the dominant Cr acceptor is found to lie at 0.69±0.02 eV from the valence band. For many of the samples, the ionized‐impurity concentrations N_I have been estimated from spark‐source mass‐spectrographic measurements and are compared with the concentrations predicted from μ_n. In general, the expected inverse relationship between μ_n and N_I is found to hold, but the scatter in the data is quite large, mainly due to the uncertainties in the mass‐spectrographic results.