Gross well‐width fluctuations in InGaN quantum wells

Abstract

AbstractIn our earlier studies, we showed that the InxGa1–xN quantum wells in some green‐emitting commercial light emitting diodes are highly non‐uniform, containing gross width fluctuations on a 50–100 nm lateral scale. We reproduced such fluctuations in a research laboratory context by either annealing the InxGa1–xN epilayer, or subjecting it to a temperature ramp prior to growth of the GaN cap. We showed that the width fluctuations relate to a network of interlinking InxGa1–xN strips, and that threading dislocations tend to intersect this network between the strips. Here we investigate whether such networks may also be formed under a range of other growth conditions. By examining very thin InxGa1–xN epilayers which are expected to be fully strained, and showing they form networks upon thermal treatment, we rule out any role of strain relaxation in network formation. By examining samples grown at temperatures up to 790 °C, with low indium contents, and observing the formation of a network structure, we eliminate the possibility that spinodal decomposition is involved in network formation. The growth conditions examined are relevant to blue and ultra‐violet light emitters, and we thus suggest that network structures may have broader implications than previously realised. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)