Mn-doping with reduced carry-over effect in semi-insulating GaN grown by MOCVD

Semi-insulating GaN layers for high-electron mobility transistors (HEMTs) used in radio frequency applications are typically achieved through Fe-doping, despite its known adverse effects on transport properties. In this paper, we investigate the possibility of using Mn as an alternative dopant to Fe for GaN buffer layers grown by metal-organic chemical vapor deposition and assess its incorporation onto the subsequent non-intentionally doped (nid) layers. For this purpose, two studies were conducted: first, epitaxial heterostructures for HEMTs were grown with varying the thickness of the nid GaN layer, while keeping the total GaN stack thickness and the Mn-doping level, followed by varying the Mn-doping level and keeping the GaN stack thickness. The Mn-doped buffer layers showed a much faster concentration decay into the subsequent nid GaN layers than Fe. The samples maintained good surface morphology and crystalline quality, and their transport properties did not degrade with different GaN stack thicknesses and doping levels, showcasing Mn as a promising dopant for semi-insulating GaN buffer layers.