Effect of growth conditions on the Al composition and quality of AlGaN film

Effects of growth conditions on Al composition and quality of AlxGa1−xN epilayer grown by low-pressure matelorganic vapor phase epitaxy (MOVPE) have been investigated. The dependences of Al composition, growth rate and quality on the NH3 flow rate, TMAl flow rate and growth temperature were studied. The Al composition and quality of AlxGa1−xN film depend not only on the TMAl flow rate, but also on the NH3 flow rate and on the growth temperature. The Al composition of AlxGa1−xN film becomes saturated when the gas-phase composition TMAl/(TMAl + TMGa) increases to 0.4, while quality of AlxGa1−xN film becomes much worse. The Al composition of AlxGa1−xN film increases with increase in the NH3 flow rate. The quality of AlxGa1−xN epilayer is improved when the growth temperature increases. Possible Al incorporation mechanism is discussed.