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 [D]/[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 [D]/[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 degrees C gives [D]/[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 degrees 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
In this work it is demonstrated how in situ high-resolution X-ray diffraction (HRXRD), performed during thermal annealing and employing a conventional laboratory source, can be used to obtain information on the evolution kinetics of very small complexes formed in an epitaxial layer. HRXRD allows the measurement of changes in the lattice parameter of the layer (i.e. the layer strain) with different annealing strategies (by linear temperature ramp or isothermal annealing). On the basis of these data and using an appropriate model, the dissolution energy values of the complexes can be extracted. The underlying idea is that every type of complex present in the layer gives a specific lattice strain which varies under annealing, allowing their evolution to be traced accurately. As an example, this methodology is applied to the study of N-H complexes formed in hydrogen-irradiated GaAs 1Àx N x /GaAs layers.research papers
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