Synthesis of superlattice InSe nanosheets with enhanced electronic and optoelectronic performance

Multilayer InSe has emerged as a promising candidate for applications in novel electronic and optoelectronic devices due to its direct bandgap, high electron mobility, and excellent photoresponse with a broad response range. Here, we report synthesis of superlattice InSe nanosheets by simple thermal annealing for the first time. The mobility is increased to 299.1 cm2 V-1 s-1 for superlattice InSe FETs and is 4 times higher than 63.5 cm2 V-1 s-1 of pristine InSe device. The superlattice InSe photodetector shows an ultrahigh responsivity of 1.7 × 104 A/W (700 nm), which is 8.5 times greater than the pristine photodetector. Superlattice InSe photodetectors hold a good photoresponse stability and rapid response time of 20 ms. The electronic and photoresponse performance improvement of superlattice InSe is attributed to higher carrier sheet density and lower contact resistance for more effective electron injection and more photogenerated carrier injection, respectively. Those results suggest that superlattice is an effective method to further improve electronic and optoelectronic properties of two-dimensional InSe devices.