Metastability of Oxygen Donors in AlGaN

Abstract

Experimental and theoretical evidence is presented for the metastability of oxygen donors in ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$. As the aluminum content increases, Hall effect measurements reveal an increase in the electron activation energy, consistent with the emergence of a deep $\mathrm{DX}$ level from the conduction band. Persistent photoconductivity is observed in ${\mathrm{Al}}_{0.39}{\mathrm{Ga}}_{0.61}\mathrm{N}:\mathrm{O}$ at temperatures below 150 K after exposure to light, with an optical threshold energy of 1.3 eV. A configuration coordinate diagram is obtained from first-principles calculations and yields values for the capture barrier, emission barrier, and optical threshold which are in good agreement with the experimental results.