【Member Papers】Xidian University --- Enhanced Photoelectric Performance of β-Ga₂O₃ Phototransistors via NH₃ Plasma Pretreatment for Ultra-Sensitive Solar-Blind UV Detection

      Researchers from the Xidian University have published a dissertation titled "Enhanced Photoelectric Performance of β-Ga₂O₃ Phototransistors via NH₃ Plasma Pretreatment for Ultra-Sensitive Solar-Blind UV Detection" in IEEE Electron Device Letters.

Introduction

      β-Ga₂O₃ has emerged as a promising candidate for solar-blind photodetectors due to its wide bandgap of 4.6-4.9 eV and high chemical stability. These advantages have driven researchers to explore various device architectures, including photodiodes and phototransistors, to meet the growing demand for high-performance solar-blind photodetectors. Contrast to photodiodes, phototransistors is particularly advantageous for weak-light detection due to their gate-controlled capacity. However, the performance of phototransistors such as dynamic response and photoelectric properties are often hindered severely by traps positioned at the dielectric/channel interface. Addressing this challenge has become a key focus in the development of high-performance phototransistors.

Abstract

      This work presents β-Ga₂O₃ phototransistors with exceptional photoelectric performance, enhanced by NH₃ plasma pretreatment prior to Al₂O₃ dielectric deposition. The devices achieve a remarkable responsivity (R) of 1.3×10⁶ A/W and a record-high detectivity (D^*) of 2.8×10¹⁹ Jones under 254 nm ultraviolet (UV) light. Rapid photoresponse is demonstrated, with a rise time (τ_r) of 90 ms and a decay time (τ_d) of 1 ms under a 1 Hz pulsed UV light source. These superior characteristics are attributed to NH₃ plasma-induced improvements at the Al₂O₃/β-Ga₂O₃ interface, including reduced trap density and enhanced dielectric adhesion. The findings provide a promising pathway to advance β-Ga₂O₃ phototransistors for ultra-sensitive, solar-blind UV detection with rapid response capabilities.

Conclusion

      This work proposes NH₃ plasma pretreatment as an effective method for enhancing the performance of β-Ga₂O₃ phototransistors, addressing the critical challenge of interface traps at the Al₂O₃/β-Ga₂O₃ interface. By chemically passivating surface defects, this approach significantly improves dielectric adhesion and reduces trap density. As a result, the phototransistors achieve a record D^∗ of 2.8 × 10¹⁹ Jones, high R of 1.3 × 10⁶ A/W, and ultra-fast photoresponse times with a τ_r of 90 ms and a τ_d of 1 ms. These results highlight the device’s exceptional sensitivity and reliability for weak-light solar-blind UV detection. Building on this foundation, incorporating high dielectric constant materials, such as HfO₂ and ZrO₂, can further enhance the photoelectric conversion efficiency of phototransistors in the future.