Study on the growth and properties of Mg doped and Mg-Si codoped p-type GaN

We have investigated the doping characteristics of Mg doped GaN films grown by metalorganic chemical vapor deposition. We have found that Mg doped GaN layer shows high electrical conductivity and good surface morphology, simultaneously, when the [Mg]/[Ga] ratio in gas phase is 7.6×10^-3. If [Mg]/[Ga] ratios exceed an optimum value of 7.6×10^-3, surface morphologies and electrical conduction properties become poor and blue emissions, considered as deep donor-to-acceptor-pair transitions in photoluminescence spectra, are dominant. Moreover, the Mg-Si codoping characteristics was explained effectively taking advantage of the concept of competitive adsorption between Mg and Si during the growth. Based on the experimental results, we suggest the methods to get a p-GaN showing high conductivity using Mg-Si codoping.