Stable, Fast UV–Vis–NIR Photodetector with Excellent Responsivity, Detectivity, and Sensitivity Based on α-In₂Te₃ Films with a Direct Bandgap

Photoelectric conversion is of great importance to extensive applications. However, thus far, photodetectors integrated with high responsivity, excellent detectivity, large phototo-dark current ratio, fast response speed, broad spectral range, and good stability are rarely achieved. Herein, we deposited large-scale and high-quality polycrystalline indium sesquitelluride (α-In2Te3) films via pulsed-laser deposition. Then, we demonstrated that the photodetectors made of the prepared α-In2Te3 films possess stable photoswitching behavior from 370 to 1064 nm and short response time better than ca. 15 ms. At a source-drain voltage of 5 V, the device achieves a high responsivity of 44 A/W, along with an outstanding detectivity of 6 × 10(12) cm H(1/2) W(-1) and an excellent sensitivity of 2.5 × 10(5) cm(2)/W. All of these figures-of-merit are the best among those of the reported α-In2Te3 photodetectors. In fact, they are comparable to the state-of-the-art commercial Si and Ge photodetectors. For the first time, we established the theoretical evidence that α-In2Te3 possesses a direct bandgap structure, which reasonably accounts for the superior photodetection performances above. Importantly, the device exhibits a good stability against the multiple photoswitching operation and ambient environment, along with no obvious voltage-scan hysteresis. These excellent figures-of-merit, together with the broad spectral range and good stability, underscore α-In2Te3 as a promising candidate material for next-generation photodetection.