Surface Passivation of IR Photodetectors Based on InSb/In $${}_{\boldsymbol{1-x}}\mathbf{Al}_{\boldsymbol{x}}$$ Sb Heterostructures

Abstract

The methods of passivating the mesastructures of photodetectors based on InSb/In\({}_{1-x}\)Al\({}_{x}\)Sb nBn heterostructures grown by molecular-beam epitaxy are studied. The mesastructures are formed by photolithography and liquid etching. Two different dielectrics, Al\({}_{2}\)O\({}_{3}\) and Si\({}_{3}\)N\({}_{4}\), are used to passivate the surface of mesastructures. It is shown that the Si\({}_{3}\)N\({}_{4}\) dielectric efficiently passivates the surface of mesastructures, and the bulk current channel is predominant, whereas the surface leakage current prevails in the Al\({}_{2}\)O\({}_{3}\) passivated mesastructures. At small reverse biases, the correlation between the current and surface area of a mesastructure is violated due to the influence of defects. Modeling the current–voltage characteristics of mesastructures at 77 K shows that the major contribution to the dark current is made by the tunneling current of electrons through the In\({}_{1-x}\)Al\({}_{x}\)Sb barrier.