Tunable normal incidence Ge quantum dot midinfrared detectors

Abstract

Midinfrared photodetectors in the 3–5 μm region were demonstrated by using molecular beam epitaxy grown self-assembled Ge quantum dots at normal incidence. The structure was a p-i-p with p-type doped Ge dots embedded in the intrinsic layer sandwiched in the two heavily p-doped regions. The dark current density at 77 K is 6.4 mA/cm2 at 1 V. The as-grown sample has a response at normal incidence in the wavelength range of 2.2 to 3.2 μm and peaked at 2.7 μm. Thermal annealing at 900 °C for 10 min shifted the peak response to 3.6 μm. Annealing effect was simulated with the interdiffusion behavior of Ge and Si atoms to explain the shift of the response wavelength.