Enhanced Performance of β ‐Ga 2 O 3 /GaN Heterojunction UV Photodetector via Introducing an Amorphous GaON Nucleation Layer in the Reverse Substitution Growth

ABSTRACT A high detectivity (∼10 16 Jones) and enhanced spectral selectivity UV photodetector of β ‐Ga 2 O 3 /GaN heterojunction is achieved by introducing an ultra‐thin GaON amorphous nucleation layer during the initial stage of the reverse substitution growth of β ‐Ga 2 O 3 . The amorphous GaON layer is formed by oxidizing the GaN surface at a low temperature of 900°C under oxygen atmosphere, which as a nucleation layer promote its oriented transformation from GaN into β ‐Ga 2 O 3 with smoother, denser surfaces at high oxidizing temperature. The β ‐Ga 2 O 3 with (‐201) preferred orientation, obtained by the introduction of the amorphous nucleation layer, displays narrower linewidths and lower root mean square of the surface roughness (7.51 nm → 4.62 nm). The concentration of oxygen vacancies in β ‐Ga 2 O 3 has been found to be significantly reduced, and the surface morphology considerably improved. Subsequently, the fabrication of metal‐semiconductor‐metal (MSM) and vertical‐structure β ‐Ga 2 O 3 /GaN heterojunction ultraviolet photodetectors was carried out. The MSM‐type device displayed a responsivity of 174 A/W and a detectivity of 1.56 × 10 16 Jones at 20 V bias, with transient response times of 0.35 ms (rise time) and 65.7 ms (decay time). The heterojunction device showed a responsivity of 14.5 A/W and a detectivity of 10 14 Jones, with transient response reaching the millisecond level.