Direct observation of the existence of localized states in InGaN quantum wells

What is it about?

The high luminescence efficience in the InGaN material is mysterious because there are so many defects (e.g. threading dislocations) in this material. The researchers proposed a localized states theory to explain such a phenomenon about twenty years ago. However, to see the localized states directly through experiment are still not reported. Although the localized theory has been widely accepted by researchers and successfully explained some experimental results. Here we measured the photoluminescence of a single InGaN quantum well emitting yellow-green light under different temperatures (viz. from 10 K to 300 K), and directly found the transiton of carriers between two different localized states, thus making the emission peak shift widely and the line-width of the spectra peak vibrate violently with temperature. We hope such a work will give a firm testimony from experiment of the existence of localized states in InGaN material. From the electroluminescence result we confirm that the localized states can obviously improve the light output performance of InGaN-based light emitting diodes (LEDs).

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Why is it important?

It gives a solid testimony of the existence of localize states in InGaN materials. We believe after this work, the localized states theory will no longer be a presumption, it will be supported directly by the experimental results.

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