Narrowing Bandgap of HfS₂ by Te Substitution for Short‐Wavelength Infrared Photodetection

Abstract Infrared photodetectors are widely used in the field of remote sensing, communications, biomedical imaging, etc. Most photodetection based on 2D transition‐metal dichalcogenides (TMDs) is limited to the visible (Vis) to near‐infrared (NIR) due to large intrinsic bandgaps (≈1.2–2 eV). Here, a bandgap engineering of HfS₂ by a tellurium (Te)‐replacement strategy is obtained via chemical vapor transport method. The bandgap values of HfS_2(1−x)Te_2x decrease from 1.7 to 0.88 eV with Te composition changing from 0 to 0.095. Few‐layer HfS_1.81Te_0.19 based field‐effect transistors exhibit a high current on/off ratio of 10⁶ and decent electron mobility of 12.6 cm² V⁻¹ s⁻¹ at room temperature. The photodetectors show a responsivity of 2 A W⁻¹ with a remarkable photocurrent of ≈3 μA and a fast response speed of 8.8/75 ms at 830 nm simultaneously. Further, the response spectrum of HfS_2(1−x)Te_2x based photodetectors is broadened from Vis to short‐wavelength infrared (SWIR), covering the free‐space laser communications wavelength and the second NIR region in medicine. Bandgap engineering of 2D TMDs proposed in this work offer a promising route to develop bandgap‐variable 2D materials for infrared photodetection applications.