Ge/Si heterostructures with Ge quantum dots for mid-infrared photodetectors

This paper presents a review of studies of the photovoltaic characteristics of Ge/SiGe/Si heterostructures containing layers of Ge quantum dots in Si and SiGe matrices. In the experiments, the elemental composition of the SiGe films and its profile, the doping level and profiles, the position of the doped layers of Si and SiGe relative to the plane of quantum dots, and the number of layers of quantum dots were varied. The results of these studies were used to implement infrared photodetector elements functioning at normal light incidence in atmosphere transmission windows of 3 ÷ 5 and 8 ÷ 12 µm. The photodetectors have a high (up to 10³) photoelectric gain, a high detection ability in the photovoltaic and photoconductive modes (up to 0.8 · 10¹¹ cm · Hz^1/2/W at a wavelength of about 4 m), and a current sensitivity of up to 1 mA/W, reach the background limited infrared performance already at a temperature of 110 K, and can be built in monolithic focal plane arrays on silicon substrates.