基于HfO_(2)插层的Ga_(2)O_(3)基金属-绝缘体-半导体结构日盲紫外光电探测器

Ga2O3-based metal-insulator-semiconductor solar-blind ultraviolet photodetector with HfO2 inserting layer

作为一种新兴的超宽带隙半导体, Ga_(2)O_(3)在开发高性能的日盲紫外光电探测器方面具有独特的优势.金属-半导体-金属结构因其制备方法简单、集光面积大等优点在Ga_(2)O_(3)日盲紫外光电探测器中得到了广泛的应用.本文在传统的金属-半导体-金属结构Ga_(2)O_(3)日盲紫外光电探测器的基础上,利用原子层沉积技术引入高介电性和绝缘性的氧化铪(HfO_(2))作为绝缘层和钝化层,制备出带有HfO_(2)插层的金属-绝缘体-半导体结构的Ga_(2)O_(3)日盲紫外光电探测器,显著降低了暗电流,提升了光暗电流比,同时提高了器件的比探测率和响应速度,为未来Ga_(2)O_(3)在高性能弱光探测器件制备提供了一种新通用策略.

Solar-blind photodetector(PD)converts 200–280 nm ultraviolet(UV)light into electrical signals,thereby expanding application range from security communication to missile or fire alarms detections.As an emerging ultra-wide bandgap semiconductor,gallium oxide(Ga_(2)O_(3))has sprung to the forefront of solar blind detection activity due to its key attributes,including suitable optical bandgap,convenient growth procedure,highly temperture/chemical/radiation tolerance,and thus becoming a promising candidate to break the current bottleneck of photomultiplier tubes.The Ga_(2)O_(3)-based solar blind PDs based on various architectures have been realized in the past decade,including photoconductive PDs,Schottky barrier PDs,and avalanche PDs.Till now,the metal-semiconductor-metal(MSM)structure has been widely used in developing photoconductive Ga_(2)O_(3) solar-blind PDs because of its simple preparation method and large light collection area.Unfortunately,despite unremitting efforts,the performance metric of reported MSM-type Ga_(2)O_(3) solar-blind PDs still lags behind the benchmark of commercial PMTs.Apparently,lack of solution to the problem has greatly hindered further research and practical applications in this field.One effective strategy for further enhancing the device performance such as detectivity,external quantum efficiency(EQE),and light-to-dark ratio heavily relies on blocking the dark current.In this work,high-quality single crystalline b-Ga_(2)O_(3) with a uniform thickness of 700 nm is grown by using a metal organic chemical vapor deposition(MOCVD)technique.Then atomic layer deposition(ALD)fabricated ultrathin hafnium oxide(HfO_(2))films(10 nm)are introduced as inserted insulators and passivation layers.The 30 nm/100 nm Ti/Au interdigital electrodes(length:2800μm,width:200μm,spacing:200μm,4 pairs)are fabricated by sputtering on the top of the film as the Ohmic contacts.Taking advantage of its novel dielectric and insulating properties,the leakage current on Ga_(2)O_(3) thin film can be effectively inhibited by the inserted ultrathin HfO_(2) layer,and thus further improving the performance of PDs.Compared with simple MSM structured Ga_(2)O_(3) PD,the resulting metal-insulator-semiconductor(MIS)device significantly reduces dark current,and thus improving specific detectivity,enhancing light-to-dark current ratio,and increasing response speed.These findings advance a significant step toward the suppressing of dark current in MSM structured photoconductive PDs and provide great opportunities for developing high-performance weak UV signal sensing in the future.