Nitrogen Vacancy as the Donor: Experimental Evidence in the Ammonia‐Assisted Molecular Beam Epitaxy of GaN

The electron density of unintentionally doped GaN can be reduced by four orders of magnitude by increasing the ammonia beam flux during molecular beam epitaxial growth, indicating that nitrogen vacancies are the donors. This is further evidenced by secondary ion mass spectroscopy measurements on the GaN films which revealed that the concentration of Si residual impurities (the major background unintentional impurity in GaN grown by metallorganic chemical vapor deposition) is far below the carrier concentration and therefore cannot be responsible for the observed background n‐type carrier density. With optimized growth parameters, stoichiometric GaN with excellent electrical and photoluminescence properties has been achieved.