Crystal Growth and Properties of Bi-doped InSe

Indium selenide (InSe), a typical layered III-VI semiconductor, has attracted intense interest owing to its high electron mobility, tunable bandgap and exceptional plastic deformation capability, enabling it a promising candidate for next-generation electronic, optoelectronic and flexible devices. Recently, the controlled growth of intrinsic InSe crystals has been well developed, whereas doping InSe crystals with a third element remains relatively scarce. In this study, intrinsic InSe crystals were grown using the Bridgman method, and high-quality Bi-doped InSe crystals were then prepared through introducing Bi during the crystal synthesis stage. Optical microscopy and scanning electron microscopy observations indicate that the as-grown Bi-doped InSe crystals exhibit a smooth surface and excellent single-crystalline characteristic. Raman spectroscopy and X-ray diffraction analyses further demonstrate that, after Bi doping, their phase structure is consistent with former intrinsic crystals, exhibiting ε-InSe phase. Chemical etching experiments reveal that the doped Bi atoms can interact with dislocation cores within the crystal, effectively suppressing their motion and significantly reducing their dislocation density. Electrical measurements show that the Bi doping markedly increases carrier concentration and mobility of InSe crystal at high temperature, which is primarily attributed to the introduction of additional free carriers and suppression of carrier scattering resulting from the reduced dislocation density. Consequently, Bi-doped InSe crystal was successfully fabricated, and its superior performance compared to the intrinsic InSe was verified. This work provides theoretical insights and experimental guidance for optimizing properties of InSe crystals in application in future devices.