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 mu m. The p(+)n(-)n(+) and p(+)nn(-)n(+) show a dark current density of 1.5 x 10(-7) A/cm(2) and 1.8 x 10(-8) A/cm(2), and a peak responsivity about 0.35 A/W and 0.40 A/W at 1.5 mu m, 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.