Formation and dissolution of D-N complexes in dilute nitrides

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 $\left[\mathrm{D}\right]∕\left[\mathrm{N}\right]$ 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 $\left[\mathrm{D}\right]∕\left[\mathrm{N}\right]=3$, 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 $250°\mathrm{C}$ gives $\left[\mathrm{D}\right]∕\left[\mathrm{N}\right]=2$ 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 $(330°\mathrm{C})$ 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.

Figure 1

(Color online) (a) (004) x-ray diffraction rocking curves of a $280\text{−}\mathrm{nm}$-thick $\mathrm{Ga}{\mathrm{As}}_{0.9873}{\mathrm{N}}_{0.0127}$ sample before (bottommost curve) and after deuterium irradiation with doses $d_{\mathrm{D}}=7\times {10}^{17}$ and $1.2\times {10}^{18}{\mathrm{cm}}^{-2}$ (middle and topmost curves, respectively). (b) Peak normalized photoluminescence spectra at $T=290\mathrm{K}$ of the same samples displayed in (a). The same laser power density was used for all samples. (c) Deuterium depth profiles derived from NRA using the ${}^3\mathrm{He}(d,p){}^4\mathrm{He}$ reaction in the sample after different D irradiation fluences. Zero on the abscissa axis indicates the sample surface The experimental spectrum of the $1.2\times {10}^{18}{\mathrm{cm}}^{-2}$ irradiated sample, with its best simulation, is shown in the inset.

Figure 2

Deuterium depth profile of a $223\text{−}\mathrm{nm}$-thick $\mathrm{Ga}{\mathrm{As}}_{0.9878}{\mathrm{N}}_{0.0122}$ $(d_{\mathrm{D}}=3.0\times {10}^{18}{\mathrm{cm}}^{-2})$ as derived from NRA using the ${}^3\mathrm{He}(d,p){}^4\mathrm{He}$ reaction. Zero on the abscissa axis indicates the sample surface. The experimental spectrum with its best simulation is shown in the inset.

Figure 3

(004) x-ray diffraction rocking curves of the same sample shown in Fig. 2 after sequential postgrowth treatments as indicated in the figure: (a) $T=250°\mathrm{C}$ and (b) $T=328°\mathrm{C}$. Annealing step intervals are equal to 120 and $30\min$ for (a) and (b), respectively.

Figure 4

(Color online) Deuterium depth profiles derived from the ${}^3\mathrm{He}(d,p){}^4\mathrm{He}$ reaction in a $223\text{−}\mathrm{nm}$-thick $\mathrm{Ga}{\mathrm{As}}_{0.9878}{\mathrm{N}}_{0.0122}$ sample at the end of the deuteration process ($\text{line}+\text{full}$ squares), at the end of the $250°\mathrm{C}$ annealing stage $(\text{line}+\text{stars})$, and at the end of the $328°\mathrm{C}$ annealing stage ($\text{line}+\text{open}$ circles). Zero on the abscissa axis indicates the sample surface.

Figure 5

(Color online) Nitrogen $K$-edge XANES spectra (fluorescence detection) of the same sample shown in the Figs. 2, 3, 4: as grown (first line from top), as deuterated with $d_{\mathrm{D}}=3.0\times {10}^{18}{\mathrm{cm}}^{-2}$ (second line from top), annealed at $T=250°\mathrm{C}$ for $13\mathrm{h}$ (third line from top), and annealed at $328°\mathrm{C}$ for $\sim 5\mathrm{h}$ (fourth line from top).

Figure 6

(Color online) [001] axial channeling dips for GaAs (stars), N (circles), and D (squares), as measured with $1.2\mathrm{MeV}$ ${\mathrm{D}}^{+}$ backscattering and ${}^2\mathrm{H}(d,p){}^3\mathrm{H}$ and ${}^{14}\mathrm{N}(d,\alpha ){}^{12}\mathrm{C}$ reactions. (a) As-deuterated sample; (b) $328°\mathrm{C}$ annealed sample. Triangles correspond to the GaAs dip of the as-grown sample. Lines are drawn only to guide the eye.