Tunable mid-infrared receiving sensors made of InxGa1-xAs/AlyGa1-yAs/AlzGa1-zAs asymmetric step quantum-well structure

Tunable mid-infrared (3∼5 μm) receiving sensors are made of an optimized In_xGa_1-xAs/Al_yGa_1-yAs/Al_zGa_1-zAs asymmetric step quantum-well structure. The sensors display photovoltaic-type photocurrent response as well as the bias-controlled modulation of the peak wavelength of the main response, which is ascribed to the Stark shifts of the intersubband transitions from the local ground states to the extended first excited states in the quantum wells, at the 3∼5.3 μm infrared atmospheric transmission window. The theoretical calculation on the linear Stark effects of the intersubband transitions between the ground and first excited states in the asymmetric step well, which was made by the method of expanding the electron wave function in terms of normalized plane wave basis within the framework of the effective-mass envelope-function theory, agree well with the corresponding experimental measurements. The values of the main properties, including photocurrent response, dark current, and blackbody receptivity, which, for example, reaches to about 1.0 × 10¹⁰ cm·Hz¹2//W at 77 K under bias of ±7 V, of the sensors have approached near to the application requirements.