High-Performance Solar-Blind Ultraviolet Photodetectors Based on β-Ga₂O₃ Thin Films Grown on <i>p</i>-Si(111) Substrates with Improved Material Quality via an AlN Buffer Layer Introduced by Metal–Organic Chemical Vapor Deposition

Abstract

We have achieved significantly improved device performance in solar-blind deep-ultraviolet photodetectors fabricated from β-Ga₂O₃ thin films grown via metal-organic chemical vapor deposition (MOCVD) on <i>p</i>-Si(111) substrates by improving material quality through the use of an AlN buffer layer. High-structural-quality β-Ga₂O₃ films with a (-201) preferred orientation are obtained after the introduction of the AlN buffer. Under 3 V bias, the dark current reaches a minimum of 45 fA, and the photo-to-dark current ratio (PDCR) reaches 8.5 × 10⁵ in the photodetector with the metal-semiconductor-metal (MSM) structure. The peak responsivity and detectivity are 38.8 A/W and 2.27 × 10¹⁵ cm·Hz^1/2/W, respectively, which are 16.5 and 230 times that without the buffer layer. Additionally, benefiting from the introduction of the AlN layer, the photodetection performance of the β-Ga₂O₃/AlN/Si heterojunction is significantly improved. The PDCR, peak responsivity, and detectivity for the β-Ga₂O₃/AlN/<i>p</i>-Si photodetector at 5 V bias are 2.7 × 10³, 11.84 A/W, and 8.31 × 10¹³ cm·Hz^1/2/W, respectively. The improved structural quality of β-Ga₂O₃ is mainly attributed to the decreased in-plane lattice mismatch of 2.3% for β-Ga₂O₃(-201)/AlN(002) compared to that of 20.83% for β-Ga₂O₃(-201)/Si(111), as well as the elimination of the native amorphous SiO_x surface layer on the Si substrate during the initial growth of oxide thin films.