High doping efficiency in p-type Al-rich AlGaN by modifying the Mg doping planes

Abstract

High doping efficiency of the Mg dopant in Al-rich AlGaN is highly desired for AlGaN based deep ultraviolet optoelectronics. In this work, the Mg doping planes were modified by a pulsed group-III source, according to first-principles calculation results on Mg substituting Al or Ga on the surface and in the bulk of Ai-rich AlGaN. The Mg-delta-doped Al_xGa_1−xN (x ∼ 0.42) layer, using a pulsed Ga source to modify the doping planes, exhibits a very high hole concentration of 8.3 × 10¹⁸ cm⁻³, which is 67% higher than that of the reference one. A record doping efficiency of 51.9% was achieved and the consequent resistivity is as low as 0.51 Ω cm. It was found that the Mg incorporation was significantly enhanced and the acceptor activation energy (E_A) was substantially reduced, contributing to the high doping efficiency. The improved incorporation is attributed to the enhanced Mg substitution for Al at the doping planes and the increased substitution for Ga in the bulk by the modification, whereas the decreased E_A is ascribed to the enlarged valence-band bending. This method provides a simple and effective way to realize efficient p-type doping of Al-rich AlGaN.