VOLTAGE-TUNABLE FAR-INFRARED PHOTODETECTOR WITH A VERY LARGE TUNING RANGE

A highly sensitive tunable far-infrared photodetector using the 1 --> 2 intersubband Stark shift in compositionally asymmetric coupled quant um cells (CACQWs) is proposed here, The operation of this device is ba sed on the infrared absorption by electrons in the ground state transi ted from the ground-state subband E(1) of the CACQW to the first-excit ed-state subband E(2). A very large variation of eigenenergy spacing D elta E(21) (E(2) - E(1)) under an applied electric field can be achiev ed. Since the infrared radiation is absorbed via the intersubband reso nance absorption (hw = E(2) - E(1)), the detected infrared wavelength can be tuned by the Delta E(21) which can be adjusted by the applied e lectric field. Based on theoretical calculations, a tuning range from 8 to 16 mu m is predicted. This tuning capability Is achieved by varyi ng the applied electric field in the 90 to - 60 kV/cm range. The absor ption coefficient is evaluated by the density-of-state formalism and a very large absorption coefficient is obtained for the proposed CACQW structure.