Nitrogen-related electron traps in Ga(As,N) layers (≤3% N)

Capacitance spectroscopy is used to examine the compositional dependence of deep levels in Si-doped Ga(As,N) layers grown on GaAs. We find two predominant electron traps at about 0.80 and 1.1 eV above the valence band edge E-V, which do not depend on composition. For N contents above 0.1% N, the concentration of the acceptor-like gap level at E-V+1.1 eV strongly increases and leads to a distinct reduction of the donor doping efficiency in Ga(As,N) layers. Based on theoretical prediction, this electron trap is tentatively associated with a split interstitial defect containing a nitrogen and an arsenic atom on the same As lattice site [(AsN)(As)]. The trap at E-V+0.80 eV likely corresponds to nitrogen dimers, i.e., two N atoms on a single As site [(NN)(As)]. When approaching the critical layer thickness, this electron trap is increasingly generated during growth. The dimer defect can be removed by rapid thermal annealing at 720 degreesC after growth, in contrast to the stable bulk level at E-V+1.1 eV. By the formation of both N-related defects, the tensile strain in Ga(As,N) is reduced. (C) 2003 American Institute of Physics.