Hydrogen-related metastable defects in passivatedn-type GaAs grown by metal-organic vapor-phase epitaxy

Undoped n-type GaAs grown by metal-organic vapor-phase epitaxy is exposed to a hydrogen or a deuterium plasma. Two dominant deep levels, having energies ${\mathit{E}}_{\mathit{c}}$-0.2 eV and ${\mathit{E}}_{\mathit{c}}$-0.57 eV, are formed after hydrogenation. Their depths into the material correspond directly with the depth to which the shallow donors have been passivated. Furthermore, isothermal annealing measurements under zero- and reverse-bias conditions reveal that the two levels are metastable. The transformations from one configuration to the other obey first-order kinetics, with the following transformation rates: ${\nu }_1$(T)=1.2×${10}^8$ exp[(-0.82 eV)/kT] and ${\nu }_2$(T)=8.0×${10}^{10}$ exp[(-0.95 eV)/kT]. We attribute the deep levels to the formation of a hydrogen-related complex. The new hydrogen complex is found to be more stable than the shallow donor-hydrogen complex.