We report a substantial increase in the quality and photoluminescence (PL) emission efficiency of In(AsN) dilute nitride alloys grown on both p-type InAs and semi-insulting GaAs substrates, in response to rapid thermal annealing. At 4 K the PL emission efficiency increases by 25 times due to a reduction in non-radiative Shockley-Read-Hall recombination originating from elimination of point defects. For annealing temperatures up to 500 °C the activation energy for thermal quenching increases by a factor of three, with no change in the residual electron concentration and mobility. Temperature dependent PL, together with X-ray diffraction measurements, reveals an improvement in compositional uniformity. Our results are significant for photonic device applications and particularly for the development of cryogenic mid-infrared photodiodes, monolithic detectors and focal plane arrays.