Capacitance-voltage and current-voltage characteristics for the study of high background doping and conduction mechanisms in GaAsN grown by chemical beam epitaxy

The temperature dependence of capacitance-voltage (C-V) and current voltage (I-V) characteristics were used to study the cause of high background doping and the underlying current transport mechanisms in GaAsN Schottky diode grown by chemical beam epitaxy (CBE). In one hand, a nitrogen-related sigmoid increase of junction capacitance and ionized acceptor concentration was observed in the temperature range 70-100 K and was attributed to the thermal ionization of a nitrogen-hydrogen-related deep acceptor-state, with thermal activation energy of approximately 0.11 eV above the valence band maximum (VBM) of GaAsN. This acceptor state is mainly responsible for the high background doping in unintentionally doped GaAsN grown by CBE. On the other hand, the I-V characteristics at different temperatures were found to deviate from the well known pure thermionic-emission mechanism. Based on their fitting at each temperature, the recombination current in the space charge region of GaAsN Schottky diode was mainly attributed to a hole trap, localized at 0.51 eV above the VBM. Given the accuracy of measurements, this result was confirmed by deep level transient spectroscopy measurements. Nevertheless, considering the Shockley-Read-Hall model of generation-recombination, the recombination activity of this defect was quantified and qualified to be weak compared with the markedly degradation of minority carrier lifetime in GaAsN material. (C) 2012 Elsevier B.V. All rights reserved.