Electrical Transport Properties of N- and P- Doped InSe: Bulk Crystals versus Exfoliated Layers
Open AccessEfficient doping of 2D materials, including carrier type, concentration, and mobility, is challenging but essential for enabling their future electronic and photonic applications. We are developing substitutional n- and p- doping of InSe semiconductor by introducing Sn and Zn, respectively, in the Bridgman bulk crystal growth. Electrical transport properties of undoped vs. n- and p- doped InSe crystals are compared by conducting Hall measurements on bulk crystals and FET transport measurements on exfoliated thin layers. Undoped InSe is intrinsically n-type in both bulk and thin-film forms, with [n]~3.5E14 cm-3 and mu values of up to 1,400 cm2 V-1 s-1 for thick layers at 300K. Carrier concentration in Sn-doped thick layers increases approximately two-fold, while the corresponding mobility reduces ~2 times at 300 K. Zn-doped InSe shows p- behavior for bulk InSe with [p]~7.9E13 cm-3 and mu~43 cm2 V-1 s-1 at 300 K, which reverts to ambipolar/n-type behavior for thin layers in FET devices.To get the most accurate field-effect mobility by InSe FET, we compare different methods of fabricated FET devices, introducing the PMMA coating layer and Electron Beam Lithography. By comparing different fabrication methods, we found that both the fabrication methods mentioned above help reduce the trapped charges of InSe channel and surface, also increase the stability and mobility value of FET.
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