Effective Passivation of Anisotropic 2D GeAs via Graphene Encapsulation for Highly Stable Near-Infrared Photodetectors.

Germanium arsenic (GeAs) as a promising two-dimensional (2D) semiconducting material has attracted extensive attention. The high carrier mobility and tunable bandgap of GeAs offer broad prospects in electronic and optoelectronic device-related applications. The unique intrinsic anisotropy arising from the low-symmetry structure can be applied in the design of new devices. However, the rapid degradation of mechanically exfoliated GeAs in the environment poses a challenge to its practical development in scalable devices. Here, an approach to stabilize the sensitive material without isolation from the ambient environment is reported. The graphene capping layer effectively suppresses environmental degradation, enabling the encapsulated GeAs photodetectors to maintain the key electronic properties for more than 3 months under ambient conditions. In addition, the regulation of the work function of graphene significantly improves the device performance. An improved responsivity of 965.07 A/W is 20 times higher than that of pure GeAs. This work provides opportunities for the practical application of GeAs and other environmentally sensitive 2D materials.