InAlN underlayer for near ultraviolet InGaN based light emitting diodes

Abstract

We report on InAlN underlayer (UL) to improve the efficiency of near ultraviolet (NUV) light emitting diodes (LEDs). While InGaN UL is commonly used in high-efficiency blue LEDs it may absorb light for shorter wavelengths. InAlN lattice-matched to GaN exhibits a bandgap of 4.6 eV. This allows alleviating absorption issues in NUV LEDs. We demonstrate that the internal quantum efficiency of 405 nm single InGaN/GaN quantum well LEDs with InAlN UL is ∼70% compared to less than 10% for LEDs without UL. Excellent I–V characteristics are achieved thanks to polarization charge screening with high doping level at the InAlN/GaN interface.

Reduced nonradiative recombination in semipolar green-emitting III-N quantum wells with strain-reducing AlInN buffer layers

“…36 Furthermore, Haller et al observe no additional reduction of the nonradiative recombination for AlInN layer thicknesses above 50 nm. 34,35 In contrast, in the present work, a reduction of the nonradiative recombination is observed when the AlInN layer thickness is changed by several hundreds of nanometers, which goes along with a significant reduction of the strain in the QW structure. Although a possible effect of indium in the buffer layer on the nonradiative recombination cannot be excluded, it does not seem to be dominating in the present study.…”

“…One might suspect that indium in AlInN itself is involved in the process of reducing defects in the QWs, as recently reported by Haller et al [33][34][35] for c-plane QWs, where a reduction in the nonradiative recombination is observed when an indium-containing underlayer grown at low temperatures is inserted before the QW structure. As mentioned in the beginning, all the samples investigated here include a similar low-temperature GaN underlayer of about 20 nm thickness.…”

Imaging Nonradiative Point Defects Buried in Quantum Wells Using Cathodoluminescence

“…A lattice-matched In 0.17 Al 0.83 N/GaN superlattice (SL) was chosen as an underlayer to bury surface defects. 21,27 Five samples with varying underlayer thickness were grown by changing the number of SL periods, n-these samples are then labelled as Pn (Fig. 1a).…”

Effect of Graded-Indium-Content Superlattice on the Optical and Structural Properties of Yellow-Emitting InGaN/GaN Quantum Wells

“…This result agreed well with the PL measurement results. The reason was that native defects such as V N were trapped by the indium atom in the pre-strained well to form the In-V N with lower energy [ 31 , 32 , 33 ]; therefore, reducing the number of defects in the subsequently grown quantum well layer. Thus, the FWHM of the PL spectrum was reduced and the non-radiative recombination lifetime was increased.…”