Two-color Infrared Focal Plane Array based on InAs/InGaAs/GaAs Quantum Dots in a Well Detectors Design

摘要

We report the first two-color 320 x 256 infrared Focal Plane Array (FPA), based on a voltage-tunable InAs/InGaAs/GaAs DWELL structure. The detectors, grown by solid source molecular beam epitaxy (MBE) comprise of a 15-stack asymmetric DWELL structure sandwiched between two highly doped n-GaAs contact layers, grown on a semi-insulating GaAs substrate. The DWELL region consists of a 2.2 monolayer deposition of n-doped InAs quantum dots (QDs) in an In_(0.15)GaAs_(0.85)As well, itself placed in GaAs. The well widths below and above the dots are 50A and 60A, respectively. The absorption region asymmetry results in a bias dependent spectral response, with the peak wavelength varying from 5.5 to 10 μm. Using calibrated black body measurements, mid-wavelength and long wavelength specific detectivities (D~*) of top-illuminated test pixels at 78K were estimated to be 7.1 x 10~(10) cmHz~(1/2)/W (V_b= 1.0V) and 2.8 x 10~(10) cmHz~(1/2)/W (V_b= 2.5V), respectively. Subsequently, a 320 x 256 QDIP FPA array was fabricated on a 30 μm pitch and was hybridized with an Indigo 9705 ROIC. Thermal imaging was successfully carried out at an estimated FPA temperature of 80K, using different optical filters between 3-5 μm, and 8-12 μm, so as to demonstrate two-color operation. The operability of the FPA was greater than 99%, and the noise-equivalent temperature difference was estimated to be less than 100 mK for f#l (3-5 μm) and f#2 (5-9 μm) optics.