Epitaxial Growth of Degenerately Doped Ga ₂ O ₃ Films on GaN (0001) as a Deep Ultraviolet Transparent Electrode for Opto‐Electronics Applications

Abstract GaN‐based deep ultraviolet (DUV) optoelectronic devices have garnered considerable attention for applications in sterilization, biological detection, and optical communications. However, the performance of current DUV optoelectronic devices is limited by the insufficient DUV transparency of conventional electrodes. In this work, the epitaxial growth of degenerately Si‐doped Ga 2 O 3 films on GaN as a promising DUV transparent electrode is reported. The 0.5% Si doped Ga 2 O 3 (n + ‐Ga 2 O 3 ) films exhibit DUV transparency exceeding 85% in the spectral range from 280 to 400 nm wavelength. Such a high DUV transparency is attributed to the ultrawide bandgap of ≈5.0 eV of the n + ‐Ga 2 O 3 film induced by the Burstein–Moss effect due to degenerate doping. Moreover, the n + ‐Ga 2 O 3 film exhibits a very low specific contact resistance of 1.96 × 10 −4 Ω cm 2 to GaN. High‐resolution X‐ray photoemission spectroscopic (XPS) study reveals that n + ‐Ga 2 O 3 forms a type‐II staggered band alignment with GaN with a low interface barrier of 0.15 eV and a narrow band bending thickness of a few nm. The small barrier, together with the degenerately doped Ga 2 O 3 film, enables excellent electrical contact at the n + ‐Ga 2 O 3 /GaN interface and low contact resistance. This work demonstrates n + ‐Ga 2 O 3 as a promising alternative for DUV transparent electrode for GaN‐based DUV devices.