Physics of defects and hydrogen in dilute nitrides

First-principles theory is capable of unveiling physical properties of the various defects in dilute nitrides. The authors discuss some of their recent results for native defects, N-N pairs, as well as for hydrogen in GaAsN and GaPN. The studies have shown that defect physics of dilute nitrides is qualitatively different from that of conventional semiconductors owing to the involvement of nitrogen. This leads to a number of phenomena ranging from the existence of a new class of intrinsic traps, such as the N-N split interstitials, As_Ga-N and V_Ga-N pairs, to a surprising modification of the fundamental bandgap by hydrogen.