Type–II superlattices base visible/extended short–wavelength infrared photodetectors with a bandstructure–engineered photo–generated carrier extractor

Visible/extended short–wavelength infrared photodetectors with a bandstructure–engineered photo–generated carrier extractor based on type–II InAs/AlSb/GaSb superlattices have been demonstrated. The photodetectors are designed to have a 100% cut-off wavelength of ~2.4 μm at 300K, with sensitivity down to visible wavelengths. The photodetectors exhibit room–temperature (300K) peak responsivity of 0.6 A/W at ~1.7 μm, corresponding to a quantum efficiency of 43% at zero bias under front–side illumination, without any anti–reflection coating where the visible cut−on wavelength of the devices is <0.5 µm. With a dark current density of 5.3 × 10 ⁻⁴ A/cm ² under −20 mV applied bias at 300K, the photodetectors exhibit a specific detectivity of 4.72 × 10 ¹⁰ cm·Hz ^1/2 /W. At 150K, the photodetectors exhibit a dark current density of 1.8 × 10 ⁻¹⁰ A/cm ² and a quantum efficiency of 40%, resulting in a detectivity of 5.56 × 10 ¹³ cm·Hz ^1/2 /W.