Mid-wavelength InAs/GaSb type-Ⅱ superlattice barrier detector with nBn design and M barrier

This study reports the performance of an InAs/GaSb type-Ⅱ superlattices(T2SLs) detector with nBn structure for mid-wavelength infrared(MWIR) detection. An electronic band structure of M barrier is calculated using 8-band k·p method, and the nBn structure is designed with the M barrier. The detector is prepared by wet etching, which is simple in manufacturing process. X-ray diffraction(XRD) and atomic force microscope(AFM) characteristics indicate that the detector material has good crystal quality and surface morphology. The saturation bias of the spectral response measurements at 77 K is 300 m V, and the device is promising to work at a temperature of 140 K. Energy gap of T2SLs versus temperature is fitted by the Varshni curve, and zero temperature bandgap Eg(0), empirical coefficients α and β are extracted. A dark current density of 3.2×10-5A/cm2and differential resistance area(RA) product of 1.0×104Ω·cm2are measured at 77 K. The dominant mechanism of dark current at different temperature ranges is analyzed. The device with a 50% cutoff wavelength of 4.68 μm exhibits a responsivity of 0.6 A/W, a topside illuminated quantum efficiency of 20% without antireflection coating(ARC), and a detectivity of 9.17×1011cm·Hz1/2/W at 77 K and 0.3 V.