We have examined the effect of growth temperature and presence of in situ grown InGaAs buffer layer on the structural, optical, and electrical properties of the InAsAs grown by low pressure methalorganic chemical deposition. The high crystalline quality InAlAs is obtained on g high quality InGaAs buffer at high temperature. For InAlAs grown at $750^{circ}C$ on InGaAs buffer at $635^{circ}C$the band-edge luminescence with the narrowest linewidth of 15 meV is observed at 1.52eV, indicating a superior quality InAlAs. The improvement of optical and electrical quality of InAlAs layer is concurrent with the enhancement of structural quality.