Short-wavelength infrared InAs/GaSb superlattice hole avalanche photodiode

We demonstrate two short-wavelength infrared avalanche photodiodes based on InAs/GaSb superlattice grown by metal-organic chemical vapor deposition. The difference between the two devices, namely, p⁺n⁻n⁺ and p⁺nn⁻n⁺, is that the p⁺nn⁻n⁺ device possesses an additional middle-doped layer to separate the multiplication region from the absorption region. By properly controlling the electric field distribution in the p⁺nn⁻n⁺ device, an electric field of 906 kV/cm has been achieved, which is 2.6 times higher than that in the p⁺n⁻n⁺ device. At a reverse bias of –0.1 V at 77 K, both devices show a 100% cut-off wavelength of 2.25 μm. The p⁺n⁻n⁺ and p⁺nn⁻n⁺ show a dark current density of 1.5 × 10⁻⁷ A/cm² and 1.8 × 10⁻⁸ A/cm², and a peak responsivity about 0.35 A/W and 0.40 A/W at 1.5 μm, respectively. A maximum multiplication gain of 55 is achieved in the p⁺nn⁻n⁺ device while the value is only less than 2 in the p⁺n⁻n⁺ device. Exponential nature of the gain characteristic as a function of reverse bias confirms a single carrier hole dominated impact ionization.