Mid-wavelength InAs/GaSb Type-II Superlattice Barrier Detector with nBn Design and M Barrier

Abstract:

This study reports the performance of an InAs/GaSb type-II superlattices (T2SLs) detector with nBn structure for mid-wavelength infrared detection. An electronic band structure of M structure is calculated using 8-band k?p method, and the nBn structure is designed with the M-barrier. Mesa isolation of the nBn structure and the removal of Al2O3 pas-sivation layer on the mesa are prepared by wet etch, which is simple in manufacturing process. X-ray diffraction (XRD) and atomic force microscope (AFM) characterization indicate that the detector material has good crystal quality and sur-face morphology. Spectral response measurements at different biases and temperatures are performed. The saturation bias is 300 mV, and the device is promising to work at a temperature of 140 K. Energy gap of T2SL versus temperatures are fitted by the Varshni curve, and zero temperature bandgap Eg(0), empirical coefficients α and β are extracted. A dark cur-rent density of 3.2?10-5 A?cm2 and differential resistance area (RA) product of 1.0 ? 104 Ω?cm2 are measured for the nBn detector at 77 K. The dominant mechanism of dark current at different temperature ranges is analyzed by calculating the activation energy according to the Arrhenius plot. The device with a 50% cutoff wavelength of 4.68 ?m exhibits a responsivity of 0.6 A/W without antireflection coating, a topside illuminated quantum efficiency of 20%, and a detectivity of 9.17?1011 cm?Hz1/2/W at 77 K and 0.3 V. Excellent performance indicates that the device is a promising candidate for large area focal plane arrays.

Key words:InAs/GaSb Type-II Superlattice，nBn，Mid-wavelength，M Barrier