M. Reinhardt

Effect of temperature on the optical properties of (InGa)(AsN)/GaAs single quantum wells

InxGa1−xAs1−yNy/GaAs single quantum wells emitting at room temperature in the wavelength range λ=(1.3–1.55) μm have been studied by photoluminescence (PL). By increasing temperature, we find that samples containing nitrogen have a luminescence thermal stability and a room temperature emission efficiency higher than that of the corresponding N-free heterostructures. The temperature dependence of the PL line shape shows a progressive carrier detrapping from localized to extended states as T is increased. Finally, the extent of the thermal shift of the free exciton energy for different y indicates that the electron band edge has a localized character which increases with nitrogen content.InxGa1−xAs1−yNy/GaAs single quantum wells emitting at room temperature in the wavelength range λ=(1.3–1.55) μm have been studied by photoluminescence (PL). By increasing temperature, we find that samples containing nitrogen have a luminescence thermal stability and a room temperature emission efficiency higher than that of the corresponding N-free heterostructures. The temperature dependence of the PL line shape shows a progressive carrier detrapping from localized to extended states as T is increased. Finally, the extent of the thermal shift of the free exciton energy for different y indicates that the electron band edge has a localized character which increases with nitrogen content.

Hydrogen-induced band gap tuning of (InGa)(AsN)/GaAs single quantum wells

The effect of atomic hydrogen on the electronic properties of (InGa)(AsN)/GaAs single quantum wells (QWs) has been investigated by photoluminescence (PL) spectroscopy. For increasing hydrogen dose, the band gap of the material increases until it reaches the value corresponding to a N-free reference QW. The band gap variation is accompanied by an increase of the line width of the PL spectra and a decrease of the PL efficiency. Annealing at 500 °C fully recovers the band gap and PL line width the sample had before hydrogenation. These results are accounted for by the formation of N–H complexes, which lowers the effective nitrogen content in the well.

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.

Optical investigations of InGaAsN/GaAs single quantum well structures

Abstract The influence of nitrogen content on the optical properties of InGaAsN/GaAs single quantum wells (SQWs) with nitrogen concentration up to 5.2% and relatively high indium content have been investigated by photoreflectance (PR) and photoluminescence (PL) spectroscopy. The PR measurements have allowed us to observe, besides of the fundamental 11H optical transition, transitions between excited states in QWs. The identification of optical transitions present in PR spectra has been possible due to the theoretical calculations based on the envelope function model. We have found the relatively high red shift of all optical transitions with increasing nitrogen content. The temperature dependence of PL peak energy have been investigated, too. The thermal stability of PL peak energy is stronger for structures with higher N content. Fitting with Varshni empirical relation to PL data we have found that at low temperatures carriers are localised. For structures with high nitrogen content we observed S-shaped energy peak behaviour.

High temperature photoluminescence efficiency and thermal stability of (InGa)(AsN)/GaAs quantum wells

The temperature dependence of the photoluminescence (PL) efficiency of (InGa)(AsN)/GaAs single quantum wells (QWs) has been studied from 10 to 500 K. The PL intensity of N-containing samples is almost constant from room temperature to 500 K, in contrast to what is observed in (InGa)As QWs grown under the same conditions. This thermal stability increases for an increase in nitrogen content. We discuss these effects in terms of strain compensation at high nitrogen concentrations.

Photoreflectance spectroscopy of InGaAsN/GaAs quantum wells grown by MBE

Abstract Highly strained In 0.28 Ga 0.72 As 1− x N x /GaAs single quantum well (SQW) structures grown by molecular beam epitaxy for different N mole fractions have been investigated by photoreflectance (PR) spectroscopy at room temperature. The influence of nitrogen on the electronic structure and on the optical properties of the quantum well has been analysed. The observation of excited state transitions allowed demonstrating a type I band line-up for both heavy and light holes, for such indium and nitrogen mole fractions. All the observed optical transitions have been identified on the base of the results of the envelope function calculation including strain effects. The dependence of the optical transitions on the nitrogen content has been derived and compared with the experiment.

ECR-MBE growth and patterning of GaInNAs/GaAs quantum wells for 1st order DFB lasers

Abstract We report on the growth, fabrication and characterization of 1st order DFB lasers on GaInNAs. A good quaternary GaInNAs layer quality could be achieved by using solid source molecular beam epitaxy and an electron cyclotron resonance source for nitrogen generation. GaInNAs QWs with nitrogen contents of about 0.5% embedded in separate confinement heterostructure lasers were pumped optically and electrically. The evanescent field of the laser mode couples strongly to the effective refractive index modulation of a DFB grating. Monomode emission peaks depending on the grating period are obtained at room temperature emitting in the 1.1 μ m range. In addition, pulsed room-temperature operation of 1.28 μ m GaInNAs broad area laserdiodes is achieved. This could be realized by increasing the nitrogen content of the active layer to about 1%.

Nitrogen-Related Complexes in Ga(AsN) and Their Interaction with Hydrogen

The effects of H irradiation on the optical properties of GaAs 1-y N y epilayers in the dilute N limit have been studied. H irradiation leads to a progressive and finally complete passivation of bound exciton levels related to N complexes. A further thermal annealing restores the optical properties that the samples had before hydrogenation. These results are accounted for by the formation of N-H complexes with different bond strengths and dissociation energies.

Reversibility of the effects of hydrogen on the electronic properties of InxGa1-xAs1-yNy

Abstract The effects of post-growth hydrogen irradiation and subsequent thermal annealing on the electronic properties of (InGa)(AsN) single quantum wells (QWs) have been studied by photoluminescence spectroscopy. We find that the QW effective band gap increases as a result of hydrogen irradiation and may reach the value it has in a N-free reference sample. Thermal annealing, instead, restores the optical properties the QW had before hydrogenation. These results are accounted for by the formation of N–H complexes, with an ensuing N passivation and a reduction of the effective N concentration. By means of isochronal annealings performed at different temperatures we determine the activation energy for the dissociation of such complexes, which has a Gaussian distribution. We attribute this finding to N clusters with different size forming different H–N bonds.