Formation and dissolution of D-N complexes in dilute nitrides

Abstract

Deuterium (hydrogen) incorporation in dilute nitrides (e.g., GaAsN and GaPN) modifies dramatically the crystal's electronic and structural properties and represents a prominent example of defect engineering in semiconductors. However, the microscopic origin of D-related effects is still an experimentally unresolved issue. In this paper, we used nuclear reaction analyses and/or channeling, high resolution x-ray diffraction, photoluminescence, and x-ray absorption fine structure measurements to determine how the stoichiometric $[\mathrm{D}]∕[\mathrm{N}]$ ratio and the local structure of the N-D complexes parallel the evolution of the GaAsN electronic and strain properties upon irradiation and controlled removal of D. The experimental results provide the following picture: (i) Upon deuteration, nitrogen-deuterium complexes form with $[\mathrm{D}]∕[\mathrm{N}]=3$, leading to a neutralization of the N electronic effects in GaAs and to a strain reversal (from tensile to compressive) of the N-containing layer. (ii) A moderate annealing at $250\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ gives $[\mathrm{D}]∕[\mathrm{N}]=2$ and removes the compressive strain, therefore the lattice parameter approaches that of the N-free alloy, whereas the N-induced electronic properties are still passivated. (iii) Finally, annealings at higher temperature $(330\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ dissolve the deuterium-nitrogen complexes, and consequently the electronic properties and the tensile strain of the as-grown GaAsN lattice are recovered. Therefore, we conclude that the complex responsible for N passivation contains two deuterium atoms per nitrogen atom, while strain reversal in deuterated GaAsN is due to a complex with a third, less tightly bound deuterium atom.