Tunneling‐Induced Amplification of Photoexcited Electrons in ITO–Graphene Heterojunction Photodetectors for High‐Performance Photodetection

In this study, we investigate the performance of an Indium tin oxide (ITO)–graphene heterojunction photoreactor, fabricated using the RF‐sputtering method. The ITO thin film, with a thickness of 23.4 nm and a grain size of 12.5 nm, was deposited onto graphene under an oxygen‐to‐argon gas ratio of 1:20. The ITO area was precisely controlled using a metal mask, resulting in an ITO–graphene heterojunction structure. The photoreactor exhibited a significant increase in current under forward bias, with a cut‐in voltage of 2.8 V and leakage current under reverse bias. Schottky junction characteristics were observed between the ITO and graphene. At −0.2 V bias, the dark current was 0.55 nA/cm 2 , while the device demonstrated high photoresponsivity (1.56 A/W) and photodetectivity (9 × 10 12 Jones). Notably, the device showed tunneling‐induced amplification of the photocurrent, approximately 44 times, due to photoelectrons tunneling from the graphene side to the ITO layer. This tunneling effect plays a crucial role in enhancing the device's performance. Additionally, the device demonstrated self‐powered operation, with rise and fall times of 0.544 and 0.613 ms, respectively, under modulated light. These findings underscore the potential of ITO–graphene heterojunctions for high‐performance photodetectors, with tunneling‐induced amplification as a key mechanism for improved photoresponse.