HYDROGEN IN GAN - NOVEL ASPECTS OF A COMMON IMPURITY

We have studied electronic structure, energetics, and migration of hyd rogen and hydrogen complexes in GaN, based on first-principles total-e nergy calculations. Our calculations reveal a number of features very different from those exhibited by hydrogen in more traditional semicon ductors such as Si or GaAs: a very large negative-ii effect (U approxi mate to 2.4 eV), the instability of the bond-center site, high energie s for hydrogen molecules, and an unusual geometry for the Mg-H complex . All of these features are shown to be a consequence of distinctive p roperties of GaN, namely, the strongly ionic nature and the large bond strength of the Ga-N bond. We propose a simple model for the negative -ii behavior, which should be valid for H in any semiconductor.