Controllable Growth of γ-In₂Se₃ and β-InSe Thin Films for High-Performance Broadband Photodetectors

The phase and stoichiometry diversity of indium selenides provides the potential for several novel applications, especially for enhancing optoelectronic performance. Therefore, the epitaxial growth of single-phase indium selenides (In2Se3 and InSe) is of particular interest, which however, is still a challenge. Herein, the controllable growth of $\gamma $ -In2Se3 and $\beta $ -InSe thin films is realized via molecular beam epitaxy (MBE) on ${c}$ -plane Al2O3 substrates. The growth mode is tuned by the incorporation or not of the Se source during the deposition process. The fabricated metal-semiconductor-metal (MSM) structured $\gamma $ -In2Se3 photodetector (PD) exhibits superior performance with a high responsivity of 44.6 A/W and a high detectivity of 1.69 $\times \,\,10^{{13}}$ Jones under blue light illumination, which is 2–3 times larger than those of $\beta $ -InSe PD. Besides, the $\gamma $ -In2Se3 PD has an ultrafast photoresponse (i.e., $\tau _{\text {r}}/\tau _{\text {d}}$ of 0.18/0.20 ms). While $\beta $ -InSe PD is sensitive to broader-spectrum from ultraviolet to near-infrared (NIR) range. Both devices possess the potential for situation-specific photodetection. Moreover, the uniform and reliable properties of the devices dispersed on the same substrate have been demonstrated, which are crucial for practical applications. This work provides an alternative route for the development of high-performance PDs based on large-area indium selenide thin films.