Coexisting multi-valence states of doped Ta into β-Ga2O3 films on B-doped mono-diamond to achieve high performance heterojunction detector

Ga₂O₃, as an ultra-wide bandgap semiconductor, has promising applications, e.g. solar-blind ultraviolet detectors, but is hindered by issues related to thermal conductivity and the P-type doping method. This study prepared P-N heterojunction via Ta-doped β-Ga₂O₃ films on B-doped mono-diamonds. We found that the multi-valence states of doped Ta coexisted in β-Ga₂O₃ films, leading to a transmittance over 90 % caused by the formation of Ta₂O₅. Moreover, the dark current was four orders of magnitude higher than the intrinsic β-Ga₂O₃ film, which was attributed to the Ga³⁺ being replaced by Ta⁵⁺. The B-doped mono-diamond exhibited a high carrier concentration of 5.08 × 10¹⁸ cm⁻³ and a low resistivity of 5.92 × 10⁻³ Ω cm due to the C⁴⁺ being replaced by B³⁺. The Ta-doped β-Ga₂O₃/B-doped mono-diamond heterojunction detector exhibited excellent photoelectric properties with a high responsivity of 64 mA/W at +10 V bias voltage, providing a novel approach for solving the β-Ga₂O₃/diamond challenge to realize high-performance detectors.