GaSe–Si Based Vertically Standing Self-Powered van der Waals Heterojunction Photodetector with Ultrahigh Responsivity and Detectivity

The 2D/3D heterojunctions between 2D layered materials and 3D Si have shown immense potential for large-scale practical applications such as highly efficient solar cells¹, and photodetectors². Until now most of the reported 2D/3D p-n heterojunction based photodetectors were limited to the combination of Si with graphene³, or with TMDCs like MoS₂⁴. There are hardly any reports available on p-n heterojunctions based on Si and TMMCs like InSe and GaSe. In the recent past, several research groups developed GaSe based photodetectors which were found to be very promising in terms of their detectivity, photoresponsivity, speed, and noise equivalent power (NEP)⁵. However, the photoresponse properties still require some improvements to find potential for commercial applications. One of the most effective ways to do that is to integrate this intrinsic p-type GaSe with the state-of-the-art silicon-based technology.<br/><br/>We report on the fabrication of a vertical 2D/3D heterojunction diode between gallium selenide (GaSe) and silicon (Si), and its photoresponse properties. Kelvin Probe Force Microscopy (KPFM) has been employed to investigate the surface potentials of the GaSe/Si heterostructure leading to the evaluation of the value of conduction band offset at the heterostructure interface. The current-voltage measurements on the heterojunction device display a diode-like nature. This is attributed to the band alignment of type-II that exists at the p-n interface. The key parameters of a photodetector such as photoresponsivity, detectivity, and external quantum efficiency have been calculated for the fabricated device and compared with other similar devices. The photodetection measurements on the GaSe/Si heterojunction diode show an excellent performance of the device with a high photoresponsivity, detectivity, and EQE value of ~2.8×10³ A/W, 6.2×10¹²Jones, and 6011, respectively, at a biasing of –5 V. Even at zero biasing, a high photoresponsivity of 6 A/W has been obtained, making it a self-powered device. Therefore, the GaSe/Si self-driven heterojunction diode holds potential applications in the field of efficient optoelectronic devices.<br/><br/><b>References </b><br/>1 A. ur Rehman, M. F. Khan, M. A. Shehzad, S. Hussain, M. F. Bhopal, S. H. Lee, J. Eom, Y. Seo, J. Jung and S. H. Lee, <i>ACS Applied Materials & Interfaces</i>, 2016, <b>8</b>, 29383–29390.<br/>2 Y. Li, C.-Y. Xu, J.-Y. Wang and L. Zhen, <i>Scientific Reports</i>, 2015, <b>4</b>, 7186.<br/>3 T. Cui, R. Lv, Z.-H. Huang, S. Chen, Z. Zhang, X. Gan, Y. Jia, X. Li, K. Wang, D. Wu and F. Kang, <i>Journal of Materials Chemistry A</i>, 2013, <b>1</b>, 5736.<br/>4 V. Dhyani and S. Das, <i>Scientific Reports</i>, 2017, <b>7</b>, 44243.<br/>5 S. Sorifi, M. Moun, S. Kaushik and R. Singh, <i>ACS Applied Electronic Materials</i>, 2020, <b>2</b>, 670–676.