Influence of electromechanical coupling on optical properties of InGaN quantum-dot based light-emitting diodes

Abstract

The impact of electromechanical coupling on optical properties of light-emitting diodes (LEDs) with InGaN/GaN quantum-dot (QD) active regions is studied by numerical simulations. The structure, i.e. the shape and the average In content of the QDs, has been directly derived from experimental data on out-of-plane strain distribution obtained from the geometric-phase analysis of a high-resolution transmission electron microscopy image of an LED structure grown by metalorganic vapor-phase epitaxy. Using continuum [Formula: see text] calculations, we have studied first the lateral and full electromechanical coupling between the QDs in the active region and its impact on the emission spectrum of a single QD located in the center of the region. Our simulations demonstrate the spectrum to be weakly affected by the coupling despite the strong common strain field induced in the QD active region. Then we analyzed the effect of vertical coupling between vertically stacked QDs as a function of the interdot distance. We have found that QCSE gives rise to a blue-shift of the overall emission spectrum when the interdot distance becomes small enough. Finally, we compared the theoretical spectrum obtained from simulation of the entire active region with an experimental electroluminescence (EL) spectrum. While the theoretical peak emission wavelength of the selected central QD corresponded well to that of the EL spectrum, the width of the latter one was determined by the scatter in the structures of various QDs located in the active region. Good agreement between the simulations and experiment achieved as a whole validates our model based on realistic structure of the QD active region and demonstrates advantages of the applied approach.

Interfacially Bound Exciton State in a Hybrid Structure of Monolayer WS2 and InGaN Quantum Dots

“…As a result, in the coupled region III free electrons in n-type WS 2 readily transfer to InGaN QDs leading to a quenching T emission in PL spectra. The band bending of InGaN QDs in the band diagram is caused by the spontaneous and piezoelectric polarization-induced electric field (31)(32)(33).…”

Surface/Interface Engineering for Constructing Advanced Nanostructured Light-Emitting Diodes with Improved Performance: A Brief Review

“…It can be proved by the experimental results that white LEDs based on dodecagonal ring structures are a platform enabling a high-efficiency warm white light-emitting source. Recently, high-performance InGaN/GaN and InGaN/AlGaN nanowire heterostructure LEDs were prepared by different research groups [88][89][90][91][92][93][94]. A schematic diagram of a nanowire LED with an InGaN/AlGaN core-shell heterostructure is shown in Figure 5.…”

Nanostructured Light-Emitters

“…Over the past few years, various metal foils (e.g., Ti, Ta) [27,91] and metal-coated substrates (e.g., Al, Pt, Ti, Mo) [28,29,[92][93][94][95][96][97] have been investigated for the growth of AlGaN nanowire UV LED structures, motivated by the excellent physical properties of metals, including thermal and electrical conductivity, light reflection, as well as flexibility. In addition, by coating a metal layer to Si substrate one can also reduce the formation of SiN x .…”

“…Additionally, an electrical resistance of 1.4 mΩ•cm was measured with a doping concentration of 5 × 10 19 cm −3 . Recently, Zhou et al demonstrated the controllable conductivity of FZ grown β-Ga 2 O 3 employing Nb as dopants [93]. By increasing the Nb doping concentrations, the electrical resistance of β-Ga 2 O 3 could be changed from 3.6 × 10 2 Ω•cm to 5.5 ×10 −3 Ω•cm, corresponding to a carrier concentration from 9.55 × 10 16 cm −3 to 1.8 × 10 19 cm −3 .…”