Two-dimensional finite-difference time-domain modeling is undertaken to study the optical behaviour of midinfrared AlInSb light-emitting diode devices with close metallic back reflectors. The location of the source and mirror is investigated in detail and optimised for peak emission at ??0 = 4 ??m. A periodic surface grating is added and it is found that greater than 98% of the light at a specific wavelength may be extracted for specific grating parameters, an enhancement of ~ 20-fold. A novel type of grating termed disordered-periodic is then studied and is shown to have a much broader spectral response with more than 50% of the power extracted across a broad wavelength range.