Growth mechanisms in GaAs-VPE at low deposition temperature

The VPE growth of GaAs in the system GaAs AsCl₃ with either H₂ or He as the Carrier gas was studied in the range of low deposition temperatures. Down to about 670 °C the growth in the H₂-system is limited by the kinetics of chlorine desorption by molecular hydrogen. The increase in growth rate at lower temperatures results from the onset of GaCl₃-desorption (disproportionation mechanism). The addition of NH₃ to the vapour phase enhances this effect. Below about 700 °C the growth rate in the GaAs AsCl₃ H₂ NH₃ system becomes comparable to that in the GaAs AsCl₃ He-system, where the GaCl₃ desorption mechanism is the only possible growth mechanism.