Near infrared avalanche photodiodes with bulk Al0.04Ga0.96Sb and GaSb/AlSbsuperlattice gain layers

We demonstrate the use of bulk Al0.04Ga0.96Sb and GaSb/AlSb superlattice as the gain material in a separate absorption/multiplication avalanche photod iode with sensitivity up to 1.74 mu m. Both gain schemes were implemented i n a molecular-beam epitaxy grown structure with a selectively doped InAs/Al Sb superlattice as the n-type layer. Hole impact ionization enhancement was observed in Al0.04Ga0.96Sb by using a two wavelength injection scheme. The superlattice gain layer device exhibited multiplication factors in excess of 300, and surface limited dark current at a level comparable to InGaAs/In AlAs devices of similar design. The superlattice gain layer was found to be more promising than its bulk counterpart due to its inherent lower dark cu rrent. (C) 1999 American Institute of Physics. [S0021-8979(99)07620-3].