Electrical and Optical Characterization of InAs/GaSb-based nBn IR Detector

Over the last several years the development of type-II Strained Layer Superlattice (SLS) infrared photodetectors has yielded devices that may offer plausible alternative technology to conventional mercury cadmium telluride (MCT)-based photodetectors. Prevailing theory predicts that SLS-based detector technologies will have several potential advantages over MCT technologies, including lower dark currents and higher operating temperatures. However, experimentally it has been found that conventional p-on-n and n-on-p SLS detectors have high dark current and thus, do not reach theoretically predicted performance benchmarks. The two prevailing contributors to this high dark current are the generation-recombination (GR) current and surface leakage currents, the latter resulting from the mesa sidewall exposure. A recently emerging technology that utilizes a uni-polar barrier design nBn has been shown to reduce dark current, while keeping the inherent advantages of SLS. Specific advantages of SLS over MCT include wavelength tunability, improved uniformity, and operability potentially at a reduced manufacturing cost. This report presents some recent experimental findings for the electrical and optical response of an nBn detector composed of an InAs/GaSb SLS absorber (n) and contacts (n) with an AlGaSb barrier (B). Results include the intrinsic determination of the diffusion current, and the GR current for the nBn device. Also presented is the optical response of the InAs/GaSb nBn detector at 77K over a broad range of operating biases. Dark current measurements over the 10K-300K temperature range were undertaken to extract the activation energies in the heterostructure.