Broadband quantum cascade detectors with a cutoff wavelength of 20 m

An InP-based photovoltaic quantum cascade detector with a cutoff wavelength of 20 mu m is reported. A wave function tailored bound-to-miniband diagonal-transition active structure is proposed for the optical detection, effectively improving the photocurrent extraction efficiency and absorption strength, reducing the dark current leakage and consequently enhancing the responsivity and detectivity. The device demonstrates a broadband response of 16-20 mu m over the operating temperature range. At 17.8 mu m, a peak responsivity of 29.6 mA/W and a Johnson noise limited detectivity of 9 x 1010 Jones is obtained with a mesa of 200 mu m x 200 mu m, while maintaining a responsivity of 3.7 mA/W at 20 mu m.