Properties of metal-insulator transition and electron spin relaxation in GaN:Si

Abstract

We investigate the properties of doping-induced metal-insulator transition in GaN:Si by means of electron spin resonance and the Hall effect. While increasing the doping concentration, Si-related bands are formed below the bottom of the GaN conduction band. The ${D}^{0}$ band of single-occupied Si donor sites is centered 27 meV below the bottom of the GaN conduction band, and the ${D}^{\ensuremath{-}}$ band of double-occupied Si states is centered at 2.7 meV below the bottom of the GaN conduction band. Strong damping of the magnetic moment occurs due to filling of the ${D}^{\ensuremath{-}}$ states at Si concentrations approaching the metal-insulator transition. Simultaneously, shortening of electron spin relaxation time due to limited electron lifetime in the single-occupied ${D}^{0}$ band is observed. The metal-insulator transition occurs at the critical concentration of uncompensated donors equal to about 1.6 $\ifmmode\times\else\texttimes\fi{}$ 10${}^{18}$ cm${}^{\ensuremath{-}3}$. Electronic states in metallic samples beyond the metal-insulator transition demonstrate the nonmagnetic character of double-occupied states.