High hole concentration in nonpolar a-plane p-AlGaN films with Mg-delta doping technique

The Mg-delta-doping technique was employed in the epitaxial growth of the nonpolar a-plane p-AlGaN films on semi-polar r-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD). The structural, morphological, and electrical properties of the nonpolar a-plane p-AlGaN epi-layers were characterized with secondary ion mass spectroscopy (SIMS), high-resolution X-ray diffraction (HR-XRD), atomic force microscopy (AFM), and Hall effect measurement, respectively. The characterization results demonstrate that the crystalline quality, the surface morphology, and the efficiency of Mg incorporation in the nonpolar a-plane p-AlGaN films could be improved significantly by optimizing the pulse time of Cp2Mg mass flow in the Mg-delta-doping process. In fact, a hole concentration as high as 1.4 × 1018 cm−3 under an average Mg incorporation density of ∼1 × 1019 cm−3 was achieved.