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p-side-down, single heterostructure n-InGaN/p-GaN light emitting diodes grown by molecular beam epitaxy exhibited stable peak emission wavelengths as long as 550 nm for current densities in excess of 100 A/cm2, and minimal efficiency droop up to 150 A/cm2 without the use of an electron blocking layer. This behavior is consistent with the formation of a two-dimensional hole gas in the n-InGaN layer and a higher barrier to electron overflow in the conduction band due to the negative polarization charge at the n-InGaN/p-GaN interface.

The incorporation of nanometer scale compositional inhomogeneities in AlGaN has a great promise for improving the performance of UV light emitting diodes based on these materials by suppressing nonradiative recombination associated with dislocations. In this article, the authors report on the growth and characterization of AlGaN containing nanometer scale compositional inhomogeneity (NCI-AlGaN) alloys deposited by plasma-assisted molecular beam epitaxy. Growth under N-limited and nearly stoichiometric growth is observed to enhance the photoluminescence intensity in AlGaN alloys by promoting the spontaneous formation of these NCI regions. This is attributed to the lower adatom mobility of group III and N species on the AlGaN layer surface under these conditions as well as the formation of beneficial surface faceting.