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High pressure studies of radiative recombination processes in nitride semiconductor alloys and quantum structures

High pressure spectroscopy is an efficient tool for verifying mechanisms of light emission. In this review high-pressure studies of recombination processes in InGaN alloys and quantum well (QW) structures: GaN/AlN, GaN/AlGaN, and near-lattice-matched GaN/AlInN are presented. The radiative recombination in nitride alloys corresponds to band-to-band transitions, thus the pressure coefficient of the photoluminescence energy dEPL/dp corresponds approximately to the pressure coefficient of the energy gap dEG/dp. In nitride polar heterostructures the built-in electric field influences strongly radiative recombination processes inducing a red shift of the photoluminescence energy. It is described by the quantum-confined Stark effect (QCSE). Applying pressure causes an increase of the electric field and consequently a decrease of dEPL/dp with respect to dEG/dp. It is also shown that dEG/dp is strongly reduced with increasing QW width. It reflects an increase in the effect of built-in electric field originating from more pronounced QCSE in wider QWs.