Role of hydrogen in III–N–V compound semiconductors
The role of hydrogen in altering the electronic properties of the InxGa1?xAs1?yNy/GaAs system has been investigated by photoluminescence (PL) spectroscopy. Several heterostructures whose nitrogen concentration, y, spans from the dilute (0.0001 ? y ? 0.001) to the alloy (0.01 ? y ? 0.052) limit have been studied. The most remarkable effects observed are a quenching of the PL lines related to exciton recombination in N complexes in the dilute limit, and a bandgap blueshift of the N-containing material towards that of the N-free reference samples in the alloy limit. Differences and similarities found between In-free and x = 0.25?0.41 samples are highlighted. In all cases, the system fully recovers by thermal annealing the optical properties it had before hydrogenation. These behaviours can be accounted for by the formation of N?H bonds, which leads to an effective electronic passivation of the N atoms in the lattice. An analysis of the annealing experiments provides some clues on the geometry of the N complexes in the dilute limit as well as an estimate of the N?H bond strength in both dilute and alloy limits. All these results show that the charge distribution around the N atoms maintains in the alloy limit the strongly localized character it has in the impurity limit.