Dual-Sided Multiband Ultraviolet Communication System Based on Ga2O3/GaN PN Junction Photodetectors

Abstract

In recent years, Ga₂O₃/GaN heterojunction ultraviolet photodetectors (PDs) have garnered considerable interest for ultraviolet (UV) communication, high-resolution imaging, and multiband photodetection. However, commercialization has been constrained by high wafer costs and simplistic device designs. This study investigates the growth of high-quality β-Ga₂O₃ films on silicon-based GaN substrates using RF magnetron sputtering by varying the growth temperatures and annealing conditions. Three device structures with ring-type, standard, and composite interdigitated electrodes were developed. The utilization of small interdigitated electrode spacing combined with an extended carrier collection length provides distinct advantages in terms of responsivity, detectivity, and response speed under self-powered conditions. Under 254 nm frontside illumination, the PDs exhibited a high responsivity of 9.18 mA/W and a detectivity of 7.71 × 10¹⁰ Jones, while 365 nm illumination yielded a responsivity of −2.99 mA/W and a detectivity of 2.51 × 10¹⁰ Jones. To further enhance detection capabilities, we removed the backside Si substrate, producing suspended membrane p–n junction PDs, enabling dual-sided detection and current polarity reversal under different UV wavelengths. After elucidating the relevant carrier transport mechanisms, a UV communication system was established using the ring-type interdigitated electrode PD. This system achieved a maximum transmission rate of 40 kbps for on–off keying modulated pseudorandom binary sequence signals under 254 nm frontside illumination and 30 kbps under 365 nm backside illumination. These results demonstrate the significant potential of Ga₂O₃/GaN p–n junction PDs for UV communication applications.