High performance foreign-dopant-free ZnO/AlxGa1−xN ultraviolet phototransistors using atomic-layer-deposited ZnO emitter layer

• Published in: Journal of alloys and compounds 2023-03, Vol.937, Article 168433
• Main Authors: Wen, Quan, Lv, Zesheng, Lai, Shiquan, Li, Leyi, Jiang, Hao
• Format: Article
• Language: English
• Subjects: ALD; AlGaN; Heterojunction phototransistor; MOCVD; ZnO
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.168433

High-performance foreign-dopant-free ZnO/AlxGa1−xN heterojunction ultraviolet (UV) phototransistors were fabricated and characterized. The ZnO layer with high electron concentration was grown as emitter by atomic layer deposition, while the AlxGa1−xN/GaN heterostructure was epitaxied as base and collector by metal organic chemical vapor deposition. A linearly upgraded/downgraded AlxGa1−xN layer was used as polarization-induced n/p type layer without dopant. The prominent feature of the resulting n+-p-n ZnO/AlxGa1−xN phototransistors is a three-stage rising spectral response matching the biological action spectrum of solar UV radiation. Moreover, the phototransistors demonstrate a low dark current of less than 1 pA at 2 V, a maximum responsivity of ∼8.7 A/W at 5 V and 300 nm, a normalized detectivity of ∼1 × 1013 Jones, and a high response speed with a rise/fall time of 3.5 μs/450 μs. This work shows a feasible and simple-process approach for developing high-performance multiband spectral response photodetectors based on different wide band gap material systems. [Display omitted] •The fabricated ZnO/AlxGa1−xN n+pn-type UV phototransistors exhibit three-stage rising spectral response covering the UVA and UVB bands and matching a biological action spectrum of solar UV radiation.•A very low dark current of less than 1 pA and a high detectivity of 1 × 1013 Jones are obtained at 2 V bias and the optical gain is 7.4 × 102 at 10 V.•The PDR of the photodetector exceeds five orders of magnitude below 2 V and remains 4-fold at 10 V.•The UV/visible rejection ratio of 300 nm/450 nm is as high as 3.1 × 104 under 0.5 V, the peak responsivity is 8.5 A/W at 5 V.•The high response speed with a rise time of 3.5 μs and a fall time of 450 μs was obtained at 3 V bias.