Nanocrystalline and Polycrystalline β‑Ga2O3 Thin Films for Deep Ultraviolet Detectors

• Published in: ACS applied electronic materials 2020-10, Vol.2 (10), p.3358-3365
• Main Authors: Pintor-Monroy, Maria Isabel, Murillo-Borjas, Bayron L, Quevedo-Lopez, Manuel A
• Format: Article
• Language: English
• ISSN: 2637-6113; 2637-6113
• DOI: 10.1021/acsaelm.0c00643

The wide band gap and high breakdown field of β-Ga2O3 single crystals and thin films have recently attracted considerable attention not only for high-power applications, fabricating devices such as transistors and diodes, but also for several other applications such as deep-UV (DUV) sensors, with a cutoff at ∼280 nm, resulting in visible-blind detectors. Currently, most of the UV- and DUV-based simple metal–semiconductor–metal (MSM) systems use interdigitated electrodes, which requires high-quality, defect-free films. β-Ga2O3 films deposited by simple methods such as magnetron sputtering are scarce, and most high-quality β-Ga2O3 thin films have been demonstrated using pulsed laser deposition (PLD) and molecular beam epitaxy (MBE). Herein, we show a comprehensive study to effectively control the structural, optical, and electrical properties of β-Ga2O3 thin films deposited by sputtering. Highly oriented polycrystalline or nanocrystalline n-type β-Ga2O3 thin films were deposited by this method and evaluated as DUV detectors using a simple MSM structure under DUV light with 254 and 232 nm wavelengths. Different structuresvarying the number of fingersare evaluated, under different light intensities and applying different electric fields. High responsivities are obtained, especially for nanocrystalline β-Ga2O3 thin films. The high responsivity for both films is attributed to self-trapped holes resulting in an internal gain. Higher responsivity is also observed for higher electric fields, lower light intensities, and a smaller number of fingers. Rise and decay times are comparable, in the range of 11–13 and 14–15 ms, respectively. Our results indicate that sputtered β-Ga2O3 thin films are promising for visible-blind DUV detectors. The paper also demonstrates simple strategies to control the crystallinity of sputtered β-Ga2O3 thin films.