Deep hole traps in N-doped p-type epilayers that had been grown by molecular beam epitaxy were studied by means of isothermal capacitance transient spectroscopy and deep-level transient spectroscopy. Two hole traps, with thermal activation energies of 0.68 and 0.85eV, were detected. These centers had large potential barrier heights to carrier capture. The thermal activation energies for capture were 0.23eV for the KT1 trap and 0.33eV for the KT2 trap. This indicated that a large lattice relaxation was introduced into hole capture and emission. A deep electron trap which was related to active N doping was identified by comparing deep-level transient spectroscopy results for n-type samples that were co-doped with Cl and N, with those for Cl-doped n-type material. A deep electron trap was found which was associated with N doping and had an activation energy that was 0.36eV below the conduction band.

K.Tanaka, Z.Zhu, T.Yao: Applied Physics Letters, 1995, 66[24], 3349-51