Tunable Doping for 2D Materials Electronics

2D materials, including layered metal chalcogenides, enable a broad range of advanced electronic applications. The ability to manipulate electrical properties by doping 2D semiconductors opens a possibility for fabricating ultra-thin p/n junctions and other two-dimensional electronic devices. However, reliable processes for reproducible doping of 2D materials are yet to be developed. This talk will survey various doping approaches of 2D semiconductors from substitutional to electrostatic to charge transfer via surface, followed by the specific example of developing controllable doping of indium selenide layers. The n- and p- type substitutional doping of InSe was conducted via single crystal Bridgman growth using Sn and Zn impurities, respectively. The concentration of Sn atoms in progressively doped n-type InSe samples varied from tens to hundreds of ppm as estimated from the X-ray fluorescence (XRF) and inductively coupled plasma mass-spectrometry (ICP-MS). Electrically active dopant concentration was assessed using van-der-Pauw Hall measurements and compared against the total Sn concentration from XRF and ICP-MS. The talk will conclude with a demonstration of employing electrically tunable indium selenide layers in a p/n homojunction photodetector.