Two‐color focal plane arrays based on self assembled quantum dots in a well heterostructure

Abstract

Novel InAs/InGaAs quantum dots-in-a-well (DWELL) infrared photodetectors are described. These detectors, in which the active region consists of InAs quantum dots embedded in an InGaAs quantum well, represent a hybrid between a conventional quantum well infrared photodetector (QWIP) and a quantum dot infrared photodetector (QDIP). Like QDIPs, the DWELL detectors display normal incidence operation without gratings or optocouplers while demonstrating reproducible “dial-in recipes” for control over the operating wavelength, like QWIPs. We report the first demonstration of a two-color infrared focal plane array based on a voltage-tunable quantum dots-in-well (DWELL) design. The active region consists of multiple layers of InAs quantum dots in an In0.15Ga0.85As quantum well. Spectral response measurements yielded a peak at 5.5 µm for lower biases and at 8–10 µm for higher biases. Using calibrated blackbody measurements, the mid-wavelength and long wavelength specific detectivity (D*) were estimated to be 7.1 × 1010 cmHz1/2 /W (Vb = 1.0 V) and 2.6 × 1010 cmHz1/2 /W (Vb = 2.6 V) at 78 K, respectively. This material was processed into a 320 × 256 array and integrated with an Indigo 9705 readout chip and thermal imaging was achieved at 80 K. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)