Rapid thermal annealing in GaNxAs1−x/GaAs structures: Effect of nitrogen reorganization on optical properties

Abstract

We report on the effect of rapid thermal annealing (RTA) on the photoluminescence (PL) properties of GaNxAs1−x/GaAs structures. In particular, a blueshift of the PL peak energy is observed when annealing the samples. The results are examined as a consequence of a RTA-induced nitrogen diffusion inside the GaNxAs1−x material rather than diffusion out of the alloy, which homogenizes initial nitrogen composition fluctuations. We propose a simple model that describes the RTA-induced blueshift of the low temperature PL peak energy. This model is in good agreement with experimental results and is consistent with recent studies in which lateral composition fluctuations in the GaNAs alloy were reported.

SPSLs and Dilute-Nitride Optoelectronic Devices

“…This implied that nitrogen preferentially reorganized in the GaNAs layers rather than diffused into the GaAs barriers. Further investigations by Grenouillet et al Grenouillet et al (2002), confirms the explanation by Buyanova et al, that nitrogen reorganizes into the narrow band gap GaNAs material rather than escapes out of it. However it is important, ofcourse, to be aware that this peculiar behaviour reflects the interplay of growth conditions, which is a whole research area of its own, as well as metastability in this system.…”

“…in terms of the physical properties of the alloy, and definitive explanations remain elusive, due, as already mentioned, in part to the sometimes contradictory nature of published results Grenouillet et al (2002);Li, Pessa, Ahlgren & Decker (2001). Two possible explanations have, so far, been proposed to account for the observed blue shift of GaNAs PL spectra with annealing.…”

“…If the degradation of PL intensity is related to defect density, then performance enhancement through the annealing-out of defects is certainly limited. Additionally, the model suggested by Grenouillet et al Grenouillet et al (2002) to explain optical performance based on composition fluctuations has been demonstrated both theoretically and experimentally Grenouillet et al (2002); Pan et al (2000) to result in a limit beyond which improvement is negligible, although some papers have shown that 'extreme' annealing can also cause samples to degrade after passing through an 'optimal' state see Hierro Hierro et al (2003), Gupta et al Gupta et al (2003) and Xin et al Xin et al (2000). The presence of hydrogen (which pacifies optically-active centers) can also confuse matters, since its incorporation during 'gas-source' and 'metal-organic' growth and subsequent out-diffusion during annealing can augment perceived improvements in optical efficiency Klar et al (2003);v H G Baldassarri et al (2001).…”

“…This, ofcourse, is partly due to the different annealing conditions and growth conditions used, but is also a strong manifestation of the metastability of this alloy system. The full implications of the metastability are just evolving and different mechanisms causing a blue shift of the band gap have been suggested Grenouillet et al (2002); Mussler et al (2003); Spruytte et al (2001b); Tournie et al (2002); Xin et al (1999). Nevertheless, all discussions and investigations, so far, have suggested that GaInNAs material system is a very promising candidate for telecoms and in particular datacom applications.…”

Core-level photoemission spectroscopy of nitrogen bonding in GaNxAs1−x alloys

“…1 Post-growth annealing is normally required to produce device quality dilute nitride material, enhancing luminescence efficiency by removing interstitial nitrogen complexes, but also causing a blueshift of the emission due to outdiffusion of nitrogen 2 or diffusion of nitrogen inside the material. 3 Evidence of non-substitutional nitrogen in GaN x As 1−x has been provided by comparison of data from high-resolution x-ray diffraction (HRXRD) and secondary ion mass spectrometry (SIMS). While SIMS measures the total nitrogen content irrespective of the location of the nitrogen atoms, HRXRD gives the change in the lattice constant caused by substitution of nitrogen on anion lattice sites.…”