Intrinsic Electronic Transport Properties and Carrier Densities in PtS2 and SnSe2: Exploration of n+‐Source for 2D Tunnel FETs.

Van der Waals 2D heterostructures are the ideal platform for tunnel field‐effect transistors (TFETs) because of dangling‐bond‐free heterointerfaces. However, the limited selection of n+‐source materials restricts 2D‐TFET research. In this study, intrinsic electron transport properties and carrier density (n) of bulk PtS2 are experimentally examined by Hall measurements to explore its use as an n+‐source material suitable for TFETs in comparison with SnSe2. Despite the similar maximum depletion widths (WDm) and apparently metallic ID–VG curves at room temperature for both bulk samples, the Hall measurements elucidate that n ≈ 3.6 × 1017 cm−3 in PtS2 is much smaller than ≈4.7 × 1018 cm−3 in SnSe2. They also reveal that this difference comes from the depth of the donor level below the conduction band. Therefore, although band‐to‐band tunneling current is successfully observed in the n‐PtS2/p‐WSe2 TFET, VG modulates the n‐PtS2 source as well as p‐WSe2 channel due to the nondegenerate doping of PtS2, resulting in a degraded subthreshold swing. The analysis of the WDm–donor concentration (ND) relation elucidates that ND is not evaluated only by WDm but is largely affected by the energy gap. The general WDm–ND relation for different energy gaps provides a guide to select 2D materials suitable for TFETs. [ABSTRACT FROM AUTHOR]