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 25arcsec. In comparison with the superlattice photodiodes on GaSb (100) substrate, the 80K dark current density at 0.2V reversed bias of the (311)B photodiodes is reduced by more than one order of magnitude. The 80K zero bias resistance (R0A) of the (311)B photodiodes is enhanced by a factor of 2.9. The 50% cutoff wavelength is extended to 10.7μm when using GaSb (311)B substrate, as compared to 10.2μm for the photodiodes on GaSb (100) substrate. The 9μm zero bias detectivity of 4.4×1010cmHz1/2/W is achieved at 80K 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.