| Abstract [eng] |
Over the last decade, performance of InGaN-based light emitting diodes (LEDs) has improved considerably to the point where they are now penetrating the outdoor and indoor general lighting. One of the key issues in the manufacture of - high efficiency nitride-based heterostructures is the control of the In-composition in the InxGa1−xN quantum wells (QWs). One common approach is to grow the GaN barriers between the QWs at a higher temperature than the InGaN QWs themselves. This high temperature barrier growth has two potential impacts: reducing the density of defects in the barrier material and altering the morphology or composition distribution of the InGaN QW itself. In this work, there was investigated a matrix of four samples, which was designed to separate the two effects: quality of GaN barrier and gross well-width fluctuations. Samples were measured by the following methods: photoluminescence (PL), time resolved photoluminescence (TRPL), differential transmission (DT) and light-induced transient gratings (LITG). It was noticed, that the lower coefficient of diffusion for samples with gross well-width fluctuations can be explained by the width of the QW reducing to zero in several places, leaving a “gap” which is filled with GaN. The higher activation energy Ea indicates the deeper localization states in samples with gross well-width fluctuations. Dependence of luminescence intensity can be written as a proportion and lower γ value in samples with gross well-width fluctuations shows, that lower density of non-radiative recombination centres exist in this region. Internal quantum efficiency and FWHM of luminescence spectra dependence on excitation intensity show, that saturation of localized states has influence on luminescence efficiency droop.  . |
