  We demonstrate a low noise short wavelength infrared (SWIR) Sb based type II
superlattice (T2SL) avalanche photodiodes (APD). The SWIR GaSb/(AlAsSb/GaSb)
APD structure was designed based on impact ionization engineering and grown by
molecular beam epitaxy on GaSb substrate. At room temperature, the device
exhibits a 50 % cut-off wavelength of 1.74 micron. The device revealed to have
electron dominated avalanching mechanism with a gain value of 48 at room
temperature. The electron and hole impact ionization coefficients were
calculated and compared to give better prospect of the performance of the
device. Low excess noise, as characterized by the carrier ionization ratio of ~
0.07, has been achieved.
