Type-II InAs/GaSb superlattices have been grown by solid-source molecular beam epitaxy on GaSb (311)B substrates. The performances of these superlattices are compared with the same structure on GaSb (100). The x-ray diffraction measurements show that InAs/GaSb superlattices on (311)B and (100) GaSb both exhibit excellent material qualities with the full width at half maximum of the zeroth-order peak within 25 arc sec. In comparison with the superlattice photodiodes on GaSb (100) substrate, the 80 K dark current density at 0.2 V reversed bias of the (311)B photodiodes is reduced by more than one order of magnitude. The 80 K zero bias resistance (R(0)A) of the (311)B photodiodes is enhanced by a factor of 2.9. The 50% cutoff wavelength is extended to 10.7 mu m when using GaSb (311)B substrate, as compared to 10.2 mu m for the photodiodes on GaSb (100) substrate. The 9 mu m zero bias detectivity of 4.4 x 10(10) cm Hz(1/2)/W is achieved at 80 K for unpassivated photodiodes on GaSb (311)B, twice as high as their (100) counterparts. Data reported here demonstrate the potential of fabricating InAs/GaSb superlattice photodiodes on GaSb (311)B substrates with improved performance. (c) 2006 American Vacuum Society.