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 (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 mV, 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 E_g(0), empirical coefficients α and β are extracted. A dark current density of 3.2×10⁻⁵ A/cm² and differential resistance area (RA) product of 1.0×10⁴ Ω·cm² are 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 9.17×10¹¹ cm·Hz^1/2/W at 77 K and 0.3 V.