Influence of Schottky metal-semiconductor contact on the responsivity of UV photodetectors with internal gain
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THE EUROPEAN PHYSICAL JOURNAL D
Regular Article
Influence of Schottky metal-semiconductor contact on the responsivity of UV photodetectors with internal gain Xuan Zhou1 , Dayong Jiang1,2,a , Man Zhao1 , Yuhan Duan3 , Nan Wang1 , Chuncai Shan1 , Qian Li1 , Meng Li1 , Xiaomiao Fei1 , and Xinjing Zhao1 1
2 3
School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, P.R. China Engineering Research Center of Optoelectronic Functional Materials, Ministry of Education, Changchun 130022, P.R. China Research Center for Space Optical Engineering, Harbin Institute of Technology, Harbin 150001, P.R. China Received 21 November 2019 / Received in final form 30 March 2020 Published online 16 June 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 Abstract. Metal-semiconductor-metal (MSM) ultraviolet photodetector is fabricated on ZnO films, prepared by radio frequency magnetron sputtering technique on quartz substrates. The ZnO photodetector shows low dark current and external quantum efficiency (EQE) due to the gain effect. The device also exhibits a near linear responsivity dependence on voltage, which gradually rise to the peak first, then fall sharply, and then slightly rise again. A physical mechanism primarily focused on the relationship between carrier (electron-hole pairs) transport and barrier height at Schottky metal-semiconductor contact is given to explain the above phenomena. It is demonstrated as a straightforward and convenient way to enhance the internal gain of the simple ZnO-based Schottky photodetectors for application in the future.
1 Introduction Recently, ultraviolet (UV) photodetectors (PDs) have been attracting more and more attention due to their huge potential for applications in missile plume early warning, flame control, air purification, space-to-space communications, etc. [1–4]. With large direct bandgap energy (∼3.37 eV), high thermal conductivity and environmental friendliness, ZnO is a promising material for applications in this filed [5–7]. Compared with emerging ZnO Schottky thin film transistors (TFTs) [8–11], in which ZnO exhibits the disadvantages of voltage bias stress instability and low mobility induced by defects [8,10], metal-semiconductormetal (MSM) PDs based on rigid substrates have many attractive advantages for practical applications, such as small size, planar device structures, fast photo-response, and simplicity in fabrication process [12–15]. As we all know, UV PDs based on a p–n junction have relatively low noise and high internal gain, however, the fabrication of stable p-type ZnO films with high conductivity is still a challenge [16–18]. On a positive note, the presence of gain has been observed in MSM structure PDs now [19,20]. Therefore, realizing MSM ZnO-based Schottky photodetectors with high internal gain in a relatively simple approach has been eagerly desired for their significance and importance in the future development of this kind of photodetector
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