Mg-hydrogen interaction in AlGaN alloys

摘要

It is well known that hydrogen passivation of Mg in Mg-doped GaN reduces free hole concentrations. While there are numerous studies of passivation of Mg in GaN, little work has been reported concerning passivation rates in AlGaN alloys. We investigated the hydrogen interaction with Mg in nitrides by measuring the intensity of the electron paramagnetic resonance (EPR) signal associated with the acceptor. The samples were isothermally annealed in sequential steps ranging from 5 min - 6.6 h between 300 and 700 ℃ in H_2:N_2 (7%: 92%) or pure N_2. The signal intensity decreased during the H_2N_2 anneal and was revived by the N_2 anneal as expected; however, the rate at which the intensity changed was shown to depend on Al concentration. In addition, while all signals were quenched at 700 ℃ in H_2:N_2, a 750 ℃ N_2 anneal reactivated only about 30% of the Mg in the alloys and 80% of the intensity in the GaN film. These data suggest that the rate of passivation and activation of Mg by hydrogen is dependent on the concentration of Al in the Al_xGa_(1-x)N layer. The EPR annealing data could prove to be beneficial in improving p-type optimization in AlGaN alloys.