Spatially localised luminescence emission properties induced by formation of ring-shaped quasi-potential trap around V-pits in InGaN epi-layers

Abstract

The correlation between surface structural and luminescence properties of InGaN epi-layers grown by metal organic chemical vapour deposition has been investigated. Ringshaped regions with high In-content are observed around V-pits by spatial resolved cathodoluminescence and energy dispersive X-ray spectroscopy. These ring-shaped regions are found to form a potential energy well with depth about 300 meV with respect to the ordinary regions, which can attract carriers and suppress non-radiative recombination. The causes of the formation of high-In-content region are discussed. This localised characteristic of carriers is supported further by power and temperature dependent photoluminescence results. The understanding of the spatially emission characteristics might be helpful to improving the internal quantum efficiency of InGaN/GaN light emitting diodes (LEDs).

Uneven AlGaN multiple quantum well for deep-ultraviolet LEDs grown on macrosteps and impact on electroluminescence spectral output

“…An MQW is generally grown on a flat surface, on which macrosteps are not normally desired, 23,24) making the MQW investigated in this work 25) unusual. As an example of QWs with uneven structures, QWs grown on v-pits were reported for InGaNbased LEDs 35,36) and QWs on macrosteps have been reported for AlGaAs on a GaAs bulk substrate. 37,38) The uneven MQW on macrosteps in this study is considered to enhance the compositional modulation, thus increasing the EL output, which is a feature of the MQW in this paper.…”

Suppression of indium-composition fluctuations in InGaN epitaxial layers by periodically-pulsed mixture of N 2 and H 2 carrier gas

“…It should be noted that the spatial extent of In phase separation is still under debate. [32][33][34] However, the dimension of the phase separation is typically on the order of a few to tens of nanometres, much smaller than the sizes of inhomogeneous regions observed in our InGaN epitaxial layers. Accordingly, strictly speaking, the effect of PPM carrier gas shown in our case is to suppress the In-composition fluctuations rather than the phase separation.…”

Investigation of amber light-emitting diodes based on InGaN/AlN/AlGaN quantum wells

“…It has been reported that InGaN MQWs have an additional lower-energy emission from V-shaped pits, i.e., a facet of the f10 11g plane. 23,24) InGaN in V-shaped pits will cause the shortening of EL wavelengths, indicating that the InGaN has a low In content. There are some reasons why the additional emission originated from the phase-separated component in InGaN.…”