Peculiarities in the pressure dependence of photoluminescence in InAlN

Kaminska, Agata and Nowakowski, Piotr and Staszczak, Grzegorz and Suski, Tadeusz and Suchocki, Andrzej and Carlin, Jean François and Grandjean, Nicolas and Martin, Robert and Yamamoto, Akio (2013) Peculiarities in the pressure dependence of photoluminescence in InAlN. Physica Status Solidi B, 250 (4). pp. 677-682. ISSN 0370-1972

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Abstract

Studies of ambient-pressure and high-pressure behavior of photoluminescence (PL) for series of InxAl1-xN layers are presented. The measured evolution of PL energy (EPL) with x is characterized by a clear decrease of EPL and exhibits a strong bowing. This dependence corresponds to the predictions of ab initio calculations of the band-gap energy changes EG with x. However, values of EPL are clearly lower than EG, for 0<x<0.3. For higher x, the measured EPL follows well the calculated EG. The experimentally determined pressure coefficient of PL energy (dEPL/dp) shows a complicated behavior for alloys with different In-content. We found a strong reduction of dEPL/dp for 0<x<0.3 and a relatively constant magnitude of this coefficient for higher x. Moreover, for the lower x region, we observed dEPL/dp that can differ even by a factor two in samples with nominally very similar In-content. The general tendency in dEPL/dp evolution with x corresponds to lower values than calculated dEG/dp for alloys with non-uniform indium distribution. We propose two not necessary independent explanations of these experimental findings. First, due to non-uniform In distribution (induced, e.g. by defects or non-homogeneous strain) both EPL and dEPL/dp are reduced. Second, a similar behavior results from an involvement of the localized states, whose formation and contribution to PL can be induced by strain and/or native defects. In both hypotheses, the strain/defect density can significantly change around x≈0.18 where InxAl1-xN layers are lattice matched to GaN template.