Effects of graphene quantum dots interlayer on performance of ZnO-based photodetectors

Abstract

In this paper, the effects of inserting graphene quantum dots (GQDs) as an interlayer between two zinc oxide (ZnO) thin films is studied comprehensively. This kind of sandwich structure offers various advantages over similar structures modified using GQDs. It is obvious that exploiting GQDs properties can thoroughly modify the optical and electrical properties of ZnO thin films. Due to the two Schottky barriers created at the interfaces, low amounts of dark current (about 127 nA) and a high signal to noise ratio (SNR) of 3.52 × 102 is measured for a sandwich structure comprised of ZnO/GQDs/ZnO (ZGZ) layers.Furthermore, the high-speed photodetector, referred in this paper, responded at least 23 times faster compared to pure ZnO (ZZ), resulting in 370 μs and 8.8 ms of response time for ZGZ and ZZ, respectively. The high amounts of responsivity and detectivity achieved by this visible-blind photodetector are other unique features this form of sandwich hybrid structures benefit from. Four orders of magnitudes enhancement in detectivity accomplished by inserting a thin film of GQDs.