First-principles studies of beryllium doping of GaN - art. no. 245205

The structural and electronic properties of beryllium substitutional accept ers and interstitial donors in GaN are investigated using first-principles calculations based on pseudopotentials and density-functional theory. In p- type GaN, Be interstitials, which act as donors, have formation energies co mparable to that of substitutional Be on the Ga site, which is an acceptor. In thermodynamic equilibrium, incorporation of Be interstitials will there fore result in severe compensation. To investigate the kinetics of Be inter stitial incorporation and outdiffusion we have explored the total-energy su rface. The diffusivity of Be interstitials is highly anisotropic, with a mi gration barrier in planes perpendicular to the c axis of 1.2 eV, while the barrier for motion along the c axis is 2.9 eV. We have also studied complex formation between interstitial donors and substitutional accepters, and be tween hydrogen and substitutional beryllium. The results for wurtzite GaN a re compared with those for the zinc-blende phase. Consequences for p-type d oping using Be accepters are discussed.