Properties of p-Type GaAs Prepared by Copper Diffusion

Abstract

Purification of arsenic by hydrogen sublimation and gallium by vacuum annealing resulted in the preparation of high resistivity (∼10⁶ ohm‐cm), n‐type GaAs crystals by the horizontal Bridgman technique. Conversion of this material to p‐type was accomplished by the inward diffusion of copper from the crystal surface. Measurements of Hall mobility as a function of hole concentration in the range, 2×10¹⁶ cm⁻³ to 3×10¹⁷ cm⁻³, at room temperature showed a dependence which is consistent with theory. The analysis suggests a lattice mobility for holes of 450 cm² V⁻¹ sec⁻¹ at 300°K. The mobility varied approximately as T^−2.3 in the range 76°–300°K. At the low temperatures the number of ionized impurities ranged from 2×10¹⁵ cm⁻³. The energy levels associated with copper in GaAs are 0.023 ev and 0.15 ev above the valence band.