D. Seghier et Hp. Gislason, Electrical characterization of Mg-related energy levels and the compensation mechanism in GaN : Mg, PHYSICA B, 274, 1999, pp. 46-49
We investigated GaN:Mg samples grown by metalorganic chemical vapor deposit
ion using various electrical measurement techniques. Annealing of as-grown
samples for different duration of time gives gradual activation of accepter
s. Conductance measurements of the annealed samples show the presence of a
hole trap with concentration directly proportional to the electrically acti
ve acceptor concentration in the samples. This trap is the shallowest one i
n our samples with activation energy 130 from the valence band. We attribut
e it to an Mg acceptor. Electron traps observed in optical deep-level trans
ient measurements have too weak concentrations to influence the free carrie
r concentration. We conclude that the hole conductivity observed in the ann
ealed GaN samples is due to thermal dissociation of hydrogen from passivate
d Mg accepters. Most of the Mg concentration in the samples however remains
electrically inactive. (C) 1999 Elsevier Science B.V. Ail rights reserved.