Enhanced Performance of Ultraviolet AlGaN/GaN Photo‐HEMTs by Optimized Channel Isolation Schemes

Abstract Solar blind ultraviolet (UV) photodetectors utilizing AlGaN/GaN high electron mobility transistor (HEMT) structure offer a very high responsivity, photo‐to‐dark current ratio (PDCR), and detectivity. However, the performance of conventional mesa‐isolated photo‐HEMT is limited due to current leakage paths through the side wall and AlGaN barrier. In this work, apart from conventional mesa‐type isolation, ion implantation and metal‐insulator‐semiconductor (MIS) schemes are adopted to isolate the channels of AlGaN/GaN photo‐HEMTs. A significant reduction in dark current is achieved for MIS photo‐HEMT of around four and three orders of magnitude as compared to those of conventional mesa‐ and ion‐implanted photo‐HEMTs, respectively. Moreover, the responsivity and PDCR of MIS photo‐HEMT are around three and four orders of magnitude higher than those of conventional mesa‐isolated photo‐HEMT. Subsequently, MIS photo‐HEMT on Si substrate has achieved a very high detectivity of 4.63 × 10¹⁶ Jones at the UV incidence wavelength of 360 nm. The results presented in this work establish the advantages of MIS photo‐HEMT over other types of photo‐HEMTs. In addition, compatibility with GaN device fabrication technology and significantly enhanced optoelectronic performance suggest AlGaN/GaN MIS photo‐HEMTs as a promising candidate for a variety of advanced UV sensing applications.