Inhibition of Mg activation in p-type GaN caused by thin AlGaN capping layer and impact of designing hydrogen desorption pathway

Thermal activation of a Mg-doped GaN layer with a thin AlGaN capping layer was investigated by means of systematic electrical characterization. Two-dimensional electron gas generated at the AlGaN/GaN interface greatly inhibited activation of the underlying Mg-doped GaN layer. This finding is attributed to the charge states of the interstitial hydrogen atoms being released from the Mg-H complexes and their diffusivity being dependent on the Fermi level position in GaN-based heterostructures. Reasonable electrically active acceptor concentration in Mg-doped GaN was achieved by designing a hydrogen desorption pathway. (author)