A deep-level transient spectroscopic study was made of Ga-doped thin films which had been grown by molecular-beam epitaxy. Two prominent deep levels were observed in all of the samples. It was found that the concentration of a trap which was detected at 0.34eV below the conduction band edge was essentially independent of the dopant concentration and was attributed to the presence of native defects that arose from Se vacancies in the films. The second level, with an activation energy of 0.26eV, exhibited a very marked doping dependence and was tentatively attributed to dopant-site (Ga on Zn-site) defects; complexed with Se vacancies. The preliminary results also indicated that planar doping significantly reduced the concentration of the Ga-vacancy complex.

S.Venkatesan, R.F.Pierret, J.Qiu, M.Kobayashi, R.L.Gunshor, L.A.Kolodziejski: Journal of Applied Physics, 1989, 66[8], 3656-60