【Member Papers】Nanjing University of Posts and Telecommunications——Ultraviolet communication system utilizing effective performance β-Ga₂O₃ photodetector

Abstract

      In recent years, solar-blind ultraviolet photodetectors (PDs) based on β-Ga₂O₃ have gained significant attention for their applications in military and commercial fields. This study explores the grain orientation and crystal quality of Ga₂O₃ films grown on sapphire substrates via RF magnetron sputtering at various growth temperatures and post-annealing temperatures. After determining optimal temperatures, we investigated the photoelectric performance of the metal/semiconductor/metal detectors with different oxygen flow ratios (0%, 5%, 10%). The PD grown in a pure Ar atmosphere exhibited the highest responsivity (48.93 A/W), remarkable detectivity (1.35 × 10¹⁴ Jones), excellent external quantum efficiency (2.39 × 10⁴%), and also rapid photoresponse time (0.118 s rise time/0.031 s decay time) under 1000  μW/cm² 254 nm light illumination. These results are attributed to the internal gain from an optimal concentration of oxygen vacancies in the well-crystallized film, without the deep-level defects typically induced under oxygen-rich conditions. Leveraging this optimized chip, we developed a deep ultraviolet communication system using a Ga₂O₃-based detector. The system achieved a data rate of 65 kbps with a pseudo-random binary sequence signals utilizing on-off keying. Additionally, using discrete multi-tone signals modulated with 32-quadrature amplitude modulation, it reached a maximum data rate of 80.65 kbps, both satisfying forward error correction threshold of 3.8 × 10⁻³. These results highlight the considerable potential of high-quality β-Ga₂O₃ solar-blind PDs for ultraviolet communication applications.

FIG. 1. XRD patterns of Ga₂O₃ thin films deposited on sapphire at different (a) growth temperatures, (b) post-annealing temperatures, and (c) oxygen flow ratio, respectively; and XPS spectra of (d) full spectra scan, (e) O 1s, and (f) Ga 2p core levels for β-Ga₂O₃ films deposited at different oxygen flow ratios.

FIG. 2. (a)–(c) I–V characteristics of β-Ga₂O₃ photodetectors grown in different oxygen flow ratios under 254 nm illumination at varying intensities. (d)–(f) Time-dependent photoresponse of three PDs under 254 nm UV light illumination. (g)–(i) Magnified plots of the rise/decay edges with corresponding exponential fitting of PDs under 254 nm illumination with a light intensity of 1000  μW/cm². (j)–(l) Responsivity, detectivity, and EQE of the three PDs as functions of light intensities at 10 V bias.

DOI：

doi.org/10.1063/5.0227397