Hydrostatic pressure: a unique tool in studies of quantum structures and light emitting devices based on group-III nitrides

In nitride heterostructures and devices, effects related to (i) polarization induced electric fields (PIEFs) and (ii) spatial segregation of indium leading to exciton/carrier localization are of major significance. However, separate investigation of these effects is not straightforward since they give rise to identical observations, such as a Stokes shift of the luminescence with respect to absorption and a blue shift of luminescence with increasing pump intensity. In this work, we review the usefulness of measurements of the hydrostatic pressure dependence of InGaN luminescence for the verification of the presence of PIEFs in quantum structures and light emitting devices. Additionally, we show that the pressure coefficient is not or only slightly sensitive to the degree of localization in the InGaN alloy. Thus, the variation of the luminescence pressure coefficient in different quantum structures can be almost entirely assigned to changes in the magnitude of internal electric field. Using this knowledge, we demonstrate how the degree of PIEF screening in InGaN based LDs can be evaluated.