A very high quantum efficiency InAs/GaSb T2SL mid-wavelength infrared （MWIR） photodetector has been grown by molecular beam epitaxy （MBE）. The T2SL detector structure material exhibited smooth surface with step-flow growth and excellent structural homogeneity. The 50% cut-off wavelength was about 5.5 μm. The peak current responsivity was 2.6 A/W corresponding to a quantum efficiency over 80% at 77 K， which was comparable to that of MCT. At 77 K， the dark current density at -50 mV bias was 1.8×10^-6 A/cm² and the resistance-area product （RA） at maximum （-50 mV bias） was 3.8×10⁵ Ω·cm². The peak detectivity was calculated to be 6.1 × 10¹² cm Hz^1/2/W.