Short-period superlattices (SLs) of GaInAs/GaNAs were grown by gas-source molecular beam epitaxy. Hall measurement shows electron mobility is improved by a factor of almost two. Improvement of electron mobility can be attributed to the smaller effective mass of the SL structure. The photoluminescence (PL) intensity is improved by rapid thermal annealing (RTA). The PL intensity of digital alloys is 2.5-3 times higher than that of the random alloy at room temperature, and the improvement is even greater at low temperature (10 K) by a factor of about 12, The optimized RTA condition for short-period SLs is 700<^>C and 10s in Nz ambient. Photoconductive decay measurements show longer carrier lift time for the: SL samples, 0.2 mus vs. 0.1 mus for the random alloy, which could be caused by charge separation due to the type-II band lineup of the GaIn0.08As/GaN0.03As SLs.