InGaN/GaN Quantum Dot Light-Emitting Diodes on Silicon with Coalesced GaN Nanowire Buffer Layer

Abstract

We demonstrate InGaN/GaN quantum dot light-emitting diodes on silicon substrates with a planar buffer layer formed by coalescing GaN nanowires. The GaN buffer layer and the light-emitting diode heterostructure were grown by plasma-assisted molecular beam epitaxy. The coalesced nanowire layer exhibits a defect density of the order of ∼10 9 cm 2 , a root-mean-square (rms) surface roughness of 0.562 nm, and excellent photoluminescence characteristics. Multiple layer In 0.23 Ga 0.77 N/GaN quantum dot light-emitting diodes grown and fabricated on the GaN/Si buffer layer exhibit strong electroluminescence at ∼477 nm with a very small blue shift of ∼2.4 nm, translating to a polarization field of ∼50 kV/cm, over the injection range applied. A droop is observed in the efficiency of the devices beyond an injection of 40A/cm 2 , most possibly due to defect-assisted Auger recombination and carrier leakage from the active region.

Monolithic InGaN Multicolor Light‐Emitting Devices

“…[ 74 ] Recently, A. Aiello et al demonstrated a QD LED utilizing a nanowire GaN buffer layer with broadband emission and an IQE of 25%. [ 75 ] Besides the study by S. J. Chua et al, progress on QD LED has stalled, as the IQE remains below 30% even after years of development.…”

“…[112][113][114] Table 1 summarizes the advantages and disadvantages of the current monolithic approaches and their suitability for display applications. Among the viable approaches, top-down nanostructuring appears to be the most feasible and cost- [32,58,73,75,84,85,90,94,96,127] and b) Reported CIE coordinates [32,33,36,[53][54][55][56]62,63,71,72,84,85,97,100,109,127] effective method for commercialization and mass production, as the fabrication is based on mature commercially available epitaxial processes, with costs as low as $10 per 2 inch wafer. [115] In contrast, approaches based on bottom-up growth require lengthy and costly re-optimization for different product lines.…”

“…Figure 10. a) Plot of reported IQE values[32,58,73,75,84,85,90,94,96,127] and b) Reported CIE coordinates[32,33,36,[53][54][55][56]62,63,71,72,84,85,97,100,109,127] on a CIE 1931 x-y chromaticity diagram for the monolithic approaches. The cross at the center in (b) indicates the white point (1=3, 1=3).…”

Anisotropic Two-Photon Excited Photoluminescence and Optical Constants of InGaN Nanowires

“…Nanostructures have great advantages over bulk or thin-film materials due to their small scale and flexibility to be fabricated by design, e.g., metamaterials. Optical absorption and photoluminescence (PL) spectroscopic studies of nanowires have revealed energy levels, quantum transitions, and the influence of size. − The IGN nanowires and quantum dots are potential candidates for integrated nonlinear optical devices directly grown on silicon. − , Preliminary studies on second harmonic generation and two-photon excitation in InGaN/GaN materials have revealed the absorption bands and crystallographic orientation. − In this work, we examined the two-photon PL excitation (PLE) spectra of IGN nanowires under different excitation light polarizations and also studied the polarization of the emitted light (Figure ). Our results revealed the anisotropic resonant excitation of nanowires under normal and parallel directions to nanowires.…”

“…20−22 The IGN nanowires and quantum dots are potential candidates for integrated nonlinear optical devices directly grown on silicon. [6][7][8]23 Preliminary studies on second harmonic generation and two-photon excitation in InGaN/GaN materials have revealed the absorption bands and crystallographic orientation. 24−26 In this work, we examined the two-photon PL excitation (PLE) spectra of IGN nanowires under different excitation light polarizations and also studied the polarization of the emitted light (Figure 1).…”