Electron traps in Ga(As,N) layers grown by molecular-beam epitaxy

Deep levels in the upper half of the band gap of strained Ga(As,N) with a GaN mole fraction of 3% are examined by deep-level transient Fourier spectroscopy on GaAs/Ga(As,N)/GaAs heterojunctions grown by molecular-beam epitaxy. In as-grown structures, we find a dominant electron trap at 0.25 eV below the conduction bandedge with a concentration above 1017 cm−3. Its capture cross section of about 10−17 cm2 for electrons is too small for an efficient nonradiative recombination center in Ga(As,N). According to theoretical predictions, this level is most likely connected with a nitrogen-split interstitial defect (N–N)As. The giant concentration of this trap can be strongly reduced by rapid thermal annealing.