Nitrogen Solubility and Induced Defect Complexes in Epitaxial GaAs:N

Abstract

Thermodynamic calculation suggests that the formation of bulk GaN pins N chemical potential ${\ensuremath{\mu}}_{\mathrm{N}}\ensuremath{\le}{\ensuremath{\mu}}_{\mathrm{N}}^{\mathrm{max}}$, resulting in low equilibrium N solubility [N] in bulk GaAs:N. In epitaxial growth, however, a fully relaxed GaN phase cannot form prior to the spontaneous formation of a N-rich layer on the surface. First-principles total-energy calculations show that in the epitaxial regime one can increase ${\ensuremath{\mu}}_{\mathrm{N}}^{\mathrm{max}}$ considerably from equilibrium ${\ensuremath{\mu}}_{\mathrm{N}}^{\mathrm{max}}$ without triggering the spontaneous formation of such a N-rich layer. This enhances [N] by 8 orders of magnitude to about $4%$ at $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}650\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ in agreement with experiments. The dominant defects at high N concentration are qualitatively different from those at low [N].