Process design of the pulse injection method for low-temperature metal organic vapor phase epitaxial growth of AlN at 800 °C

The pulse injection (PI) growth method in which trimethylaluminium (TMAl) and NH3 are alternately supplied was used to grow AlN layer at 800 °C. It was found that the process parameters in the PI method such as TMAl supply time (τTMAl), TMAl partial pressure (PTMAl), and 1st H2 purge time (τH1) had great influence on the crystal quality and surface morphology. Control of the growth rate to 1 monolayer (ML)/cycle resulted in highly improved crystal quality. 3.91×10−4 mbar of PTMAl and 1 s of τH1 were also found to be very effective in realizing high crystal quality showing narrow (0 0 0 2) and (1 0 1¯ 2) full-width at half-maximum (FWHM) values confirmed by high-resolution X-ray diffraction (HRXRD) rocking curve measurement. This is because the agglomeration of initial AlN islands and adducts formation by the gas-phase reaction could be suppressed under these conditions. According to the second ion mass spectroscopy (SIMS) measurement for the AlN layer grown by PI method (PI-AlN), the impurities concentrations of hydrogen, carbon, and oxygen showed several times lower levels than those of AlN layer grown by the conventional continuous method (C-AlN) at same 800 °C. Moreover, the impurities concentrations in PI-AlN layer were almost same with those of C-AlN grown at 1240 °C. It clearly shows the effectiveness of PI method in enhancing reduction reaction by NH3.