Enhanced hole concentration in nonpolar a-plane p-AlGaN film with multiple-step rapid thermal annealing technique

An innovative multiple-step rapid thermal annealing (RTA) technique was developed for obtaining high hole concentration in the nonpolar a-plane Mg-delta-doped AlGaN films grown on semi-polar r-plane sapphire substrates with metal organic chemical vapor deposition. The structural, optical, and electrical properties of the nonpolar a-plane p-AlGaN epi-layers were characterized with high-resolution x-ray diffraction, photoluminescence spectra, and Hall effect measurement. The characterization results demonstrated that the dissociation efficiency of the Mg–H bonds in the nonpolar a-plane p-AlGaN films could be improved significantly with the multiple-step RTA process. In fact, a hole concentration as high as 1.9 × 1018 cm−3 was achieved with the multiple-step RTA technique, which was 35%, 9%, and 23% higher than those obtained with conventional one-step, two-step, and the recently renovated two-step RTA methods, respectively.