Growth of thick AlN layers by hydride vapor-phase epitaxy

Growth of AlN on sapphire (0 0 0 1) substrates by hydride vapor-phase epitaxy (HVPE) was investigated using AlCl3 and NH3 as source gases in the temperature range from 950 to 1100 °C. It was found that the full-width at half-maximum (FWHM) values of the X-ray diffraction (XRD) rocking curves of the (0 0 0 2) and (101¯0) planes of the c-axis oriented AlN layers decreased with increasing growth temperature. An AlN layer showing a mirror-like surface could be grown at 1100 °C with a growth rate of 1.7 μm/h. Growth rate was found to increase with increasing AlCl3 input partial pressure and with decreasing distance (L) between the end of the AlCl3 injection nozzle and the sapphire substrate. The growth rate reached 122 μm/h with an AlCl3 input partial pressure of 2.0×10−3 atm and L=25mm but the crystalline quality became poor when the growth rate rose above 10 μm/h.