Thickness-Modulated Band Engineering for Low-Resistance Contacts in Ultrathin Tellurium Transistors

Tellurium (Te) is increasingly gaining attention as a scalable p-type channel material owing to its inherently high carrier mobility and ambient stability. However, in sub-5 nm Te channels, high contact resistance remains a major obstacle to achieving high-performance device operation. In this study, an estimated contact resistance of ≈1.7 kΩ·μm is obtained in 4 nm-thick Te channels by engineering the band structure in the source and drain (S/D) regions using a raised source and drain (RSD) structure. To isolate intrinsic contact behavior, electrical measurements are conducted at 77 K, in which thermally activated defect states are suppressed, and carrier injection is dominated by the metal-semiconductor interface. Transport characterization reveals a more than 17-fold increase in on-state current and a more than 50-fold reduction in contact resistance relative to Te devices without the RSD structure. This enhancement is attributed to selectively increasing the Te thickness at the S/D terminals, which tunes the bandgap by thickness-dependent modulation. The resulting RSD architecture enhances tunneling current by narrowing the barrier width─modulated by gate bias. This scalable, low-temperature approach offers broad applicability to other ultrathin channel materials.