The trade-off between electrical performance and structural quality in silicon (n-type) and magnesium (p-type)-doped a-plane gallium nitride (GaN) on r-plane sapphire

Abstract This work presents a systematic study of silicon (Si) and magnesium (Mg) doping effects on the structural and electrical properties of non-polar a-plane (11̅20) GaN grown on r-plane (1̅102) sapphire by metal–organic chemical vapor deposition. Compared with conventional c-plane GaN, a-plane GaN eliminates internal polarization fields, making it attractive for optoelectronic applications. N-type and p-type layers were doped using disilane (Si₂H₆) and bis(cyclopentadienyl)magnesium (Cp₂Mg), respectively. Atomic force microscopy (AFM) revealed increased surface roughness with dopant incorporation, while high-resolution X-ray diffraction (XRD) indicated higher basal stacking fault densities at elevated doping levels. Hall Effect measurements showed maximum carrier concentrations of 4.94 × 10 19 cm −3 for electrons and 2.13 × 10 18 cm −3 for holes. Correspondingly, the specific contact resistivity decreased to 8.88 × 10 −5 Ω·cm 2 for n-type and 2.28 × 10 −3 Ω·cm 2 for p-type GaN. These results highlight the trade-off between electrical enhancement and structural degradation, providing guidelines for optimizing non-polar GaN epitaxy.