δ-Doped MOS Ge/Si quantum dot/well infrared photodetector

Metal-oxide-semiconductor tunneling diodes can be used as photodetectors at the inversion bias. To increase the responsivity, δ-doping is used in the quantum dot infrared photodetectors (QDIPs) and quantum well infrared detectors (QWIPs). The peak responsivity of the quantum dot and quantum well infrared photodetector at 15 K is found to be 0.03 mA/W and 1.3 mA/W, respectively, at a gate voltage of 1 V. The higher responsivity of the QWIP is probably due to the continuous two-dimensional density of states and smaller transition energy as compared to the QDIP. The QD photoresponse in the peak wavelength range 3.5–5 μm can be measured up to 100 K, while that for QW 3–7 μm can only be detected up to 60 K. A higher dark current due to the lower transition energy in the QWIP limits its operating temperature as compared to the QDIP.