Electrical, optical, and structural properties of Ga-doped ZnSe grown by molecular beam epitaxy

Abstract

Undoped and Ga-doped ZnSe films have been grown on (100) GaAs substrates by molecular beam epitaxy. Measurements of photoluminescence, Hall mobilities, and X-ray diffraction for these films have been made. Uniform Ga-doping is possible up to the net carrier concentration of 5 × 10 17 cm −3, resulting in low-resistivity films. The compensation ratio ranges from 0.8 to 0.96. If higher doping concentration is attempted an excessive Ga incorporation into the lattice generates a large number of defects. These defects are evidenced by photoluminescence as strong emission from Ga Zn-V Zn complexes and donor-acceptor-pair bands. At the same time, the carrier concentration and Hall mobility drastically decrease from their values for less compensated ZnSe. The lattice mismatch for ZnSe of less than 4 μn in thickness varies from 1100 to 1300 ppm, indicating that the lattice is not fully relaxed. This lattice mismatch is independent of Ga doping. The (100) Bragg planes of ZnSe are slightly tilted, about 100–200 arc sec, with respect to those of GaAs.