Tunable mid-infrared photodetectors employing Stark shifts of intersubband transitions in In 0.05Ga 0.95As/Al 0.32Ga 0.68As/Al 0.45Ga 0.55As asymmetric step quantum wells

Abstract

Tunable mid-infrared (3–5 μm) photodetectors made of In 0.05Ga 0.95As/Al 0.32Ga 0.68As/Al 0.45Ga 0.55As asymmetric step multiple quantum wells are reported. The detectors exhibit photovoltaic-type photocurrent response with the peak wavelengths modulated by an applied bias in the 3–5.3 μm infrared atmospheric transmission window. The bias-controlled modulation of the peak wavelength of the main response is due to the Stark shifts of the intersubband transitions from the ground states to the first excited states in the quantum wells. By expanding the electron wavefunction in terms of the normalized plane wave basis within the framework of the effective-mass envelope-function approximation, a theoretical calculation of the linear Stark effects of the intersubband transitions between the ground and the first excited states in the asymmetric step wells is carried out and the results agree well with experimental measurements. The key features of the photodetectors, including the photocurrent response, dark current, and black-body detectivity, which is about 1.0×10 10 cm Hz 1/2/W at 77 K under a bias of ±7 V, are close to the requirements for practical applications.