IMPURITY DEPENDENCE ON HYDROGEN AND AMMONIA FLOW-RATES IN INGAN BULK FILMS

H, C, and O impurity concentrations in metalorganic chemical vapor dep osition grown InGaN were found to be dependent on the hydrogen and NH3 flow rates. By increasing the hydrogen flow rate from O to 100 seem, a decrease of greater than two orders of magnitude in the C and O impu rity levels and one order of magnitude in the H impurity level was obs erved. Increasing the NH3 flow rate from 1 to 5 sim results in a decre ase in the C concentration and an increase in the H and O concentratio ns indicating that high purity NH3 (99.999%) can be a significant sour ce of O contamination. Additional studies show that when the InN perce nt in the InGaN films increases, the impurity concentrations increase regardless of changes in the growth conditions. The InGaN films were g rown from 710 to 780 degrees C and the impurity concentrations were ch aracterized by secondary ion mass spectrometry. (C) 1997 American Inst itute of Physics.