HYDROGEN IN GALLIUM NITRIDE GROWN BY MOCVD

The role of hydrogen in gallium nitride was studied on thin Films of G aN on sapphire prepared at substrate temperatures in the range of 600 to 1100 degrees C. By using triethylgallium and ammonia as precursor a nd hydrogen and/or nitrogen as transport gases, we have observed a str ong influence of molecular hydrogen on the deposition rate and the str uctural properties of epitaxial GaN. By elastic recoil detection analy sis and thermal desorption measurements we were able to determine the total concentration of nitrogen, hydrogen and carbon in the bulk mater ial. Isotope substitution of hydrogen by deuterium in the H-2 carrier gas did not give rise to a noticeable deuterium incorporation, showing that the sources for hydrogen are the metalorganic precursor, ammonia or reaction products of both. Once incorporated: thermally activated hydrogen effusion from n-type GaN occurs with an activation energy of more than 3.9 eV. With the help of mass spectrometry we established hy drogen effusion from heavily magnesium-doped (2 at%) GnN at temperatur es between 600 and 700 degrees C, which is the temperature range used for acceptor activation.