Au-In Alloy for Excellent Ohmic Contact in GeSe Devices with Enhanced Photodetector Properties

Metal-semiconductor contact plays a significant role in devices such as transistors, photoemitters, and photodetectors. Here, the AuIn alloy contact gives a state-of-the-art low R_C (contact resistance) in GeSe devices. The R_C of GeSe-AuIn is measured to be 25 kΩ μm under channel carrier concentration around p = 2.490 × 10¹⁰ cm^-2. This low R_C is ascribed to a small barrier height of 16 meV. Our density functional theory calculation found the formation of a high conductive metallic GeSe-AuIn interface due to indium doping, which screens the possible interface disorder-induced gap states and metal-induced gap states that are observed when using pure In (indium) or Au (gold) metal. The GeSe-AuIn photodetectors show enhanced photoresponsivity with a specific photoresponsivity of 6.46 × 10⁴ A/W and a detectivity of 8.9 × 10¹³ Jones (at 450 nm wavelength). Our study is helpful in designing high-performance GeSe-based devices.