Abstract
The authors report a 40-period (In,Ga)As/GaAs normal-incidence quantum dot infrared photodetector operating in the wavelength range 8–14 µm. A primary intersubband transition peak is observed at a wavelength of 12.5 µm (E0 → E1), and a secondary peak at 11.3 µm (E0 → E2). The measured intersubband energy spacing is in good agreement with calculations. The normal-incidence peak responsivity at the bias voltage of –6 V is ~0.17 A/W. The background-limited performance temperature of our devices is found to be 62 K.