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The effects of negative polarization charge at the n-InGaN∕p-GaN interface on the performance of hydride vapor phase-epitaxy deposited single heterostructure n-InGaN∕p-GaN LEDs with p-side down are investigated. The strong peak emission wavelength blueshift and concomitant superlinear increase in light output as the injection current increases below 25A∕cm2 are characteristic of radiative tunneling. We show that the combination of two-dimensional hole gas formation on the n-InGaN side of the heterointerface and enhancement of the electron barrier to transport across this interface results in only ∼10% efficiency droop up to 500A∕cm2 without implementation of an AlGaN electron-blocking layer or a second heterointerface.

In this paper we report 3‐7 μm thick p‐GaN growth by hydride vapor phase epitaxy (HVPE) on sapphire substrates. Mg impurity was used for doping. As‐grown GaN layers had p‐type conductivity with concentration NA‐ND up to 3×1019 cm–3. Mg atom concentration was varied from 1017 to 1020 cm–3. Hydrogen concentration was about 10 times less than that for Mg, which may explain effective p‐type doping for as‐grown GaN layers. Micro‐cathodoluminescence revealed a columnar‐like structure of the GaN layers with a non‐uniform distribution of material regions having dominant 362 nm or 430 nm luminescence. Use of these thick p‐GaN layers to grow InGaN‐based blue and green LEDs by the HVPE is demonstrated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)