Suppression of Dark Current on AlGaN/GaN Metal–Semiconductor–Metal Photodetectors

This paper proposes the H₂O₂ oxidation technique to grow Al₂O₃ as the surface passivation layer of the metal-semiconductor-metal ultraviolet (UV) photodetector (PD). The dark current of the H₂O₂-grown-Al₂O₃-passivated PD was reduced from 104 to 4.43 nA. The surface leakage of the PD was reduced from 65.7 nA/1.67 μA to 0.46 nA/0.5 nA in the dark/under illumination. It was found that ~35% photocurrent results from the surface leakage. The surface leakages in the H₂O₂-grown-Al₂O₃ passivated and the plasma-enhanced chemical vapor deposition (PECVD)-grown-SiO₂ passivated PDs were reduced significantly. Although the photocurrent and the photoresponsivity of the oxide-passivated PDs were lower than those of the unpassivated one, the dark current, UV-to-visible rejection ratio, noise equivalent power, and the detectivity of the oxide-passivated PDs were better than those of the unpassivated one. In addition, the performances of the H₂O₂-grown-Al₂O₃ passivated PD were better than those of the PECVD-grown-SiO₂ passivated one.