Enhanced photoresponse in Te/Bi2Se3/n-Si heterojunctions at visible and telecommunication wavelengths

Elemental Tellurium gained particular attention in recent years due to its properties as high mobility, p-type semiconductor and strong infrared light absorber. Its van der Waals structure allows the combination with silicon as well as with two-dimensional materials giving rise to stacked structures with novel electronic and optical properties. Here we report a method to enhance photodetector performances, in terms of photocurrent and response speed at visible and infrared wavelengths, of Te/n-Si heterojunctions by introducing a topological insulator buffer layer of Bi 2 Se 3 between Te and n-Si substrate. The photocurrent of the obtained stacked structure Te/Bi 2 Se 3 /n-Si results respectively 2.7 and 59 times higher than that shown by Bi 2 Se 3 /n-Si and Te/n-Si at λ = 1550 nm when operating in self-powered mode. Moreover, the response time at visible wavelength decreases up to 6 times with respect to Te/n-Si and 2.9 times to Bi 2 Se 3 /n-Si. The obtained results are ascribed to the presence of the high mobility surface states of Bi 2 Se 3 topological insulator. The research confirms the success in combining different nanomaterials for wide range wavelength optoelectronic devices and in the use of topological insulators for fast photodetectors.