Structural, Optical, and Electrical Characterization of 643 nm Red InGaN Multiquantum Wells Grown on Strain‐Relaxed InGaN Templates

Abstract

Red‐emitting (≈643 nm) InGaN multiquantum well active device layers and micro‐LEDs are grown by metal organic chemical vapor deposition (MOCVD) on relaxed InGaN templates, the latter created via thermal decomposition of an InGaN underlayer, and examined via power‐ and temperature‐dependent photoluminescence and electrical measurements. Maximum internal quantum efficiencies are determined to be 7.5% at an excitation power density of 13 W cm−2, radiative recombination occurs through monomolecular recombination, and the fabricated micro‐LEDs do not show any efficiency degradation with decreasing size. Peak on‐wafer external quantum efficiency (EQE) of a 5 × 5 μm2 device is 0.44%, demonstrating that thermally decomposed InGaN “strain‐relaxing” underlayers may be useful for long wavelength micro‐LED applications.

Significant reduction in sidewall damage related external quantum efficiency (EQE) drop in red InGaN microLEDs (∼625 nm at 1 A cm−2) with device sizes down to 3 μm

“…25) In 2020, 26) Pasayat et al demonstrated 0.2% on-wafer EQE for a 6 μm × 6 μm device at 10 A cm −2 emitting at 632 nm using porous GaN technology. 27) Other efforts in red InGaN microLEDs include use of a relaxed InGaN pseudosubstrates from SOITEC, 28,29) a thermal decomposition layer [30][31][32][33] and by using hybrid multiple quantum wells (MQW) stack. [34][35][36] Size independent EQE has been previously demonstrated 37) for InGaN based red microLEDs from 80 μm × 80 μm devices down to 20 μm × 20 μm devices.…”

Recent advances in micro-pixel light emitting diode technology

“…This behavior could be attributed to suppressed surface recombination and increased LEE via the sidewall. Similarly, Lim et al 67 investigated InGaN-based red lLEDs using thermal decomposition to relax the strain and found that the EQE peak of red lLEDs increased as their size decreased from 100 Â 100 to 5 Â 5 lm 2 . These results indicate that InGaN-based red lLEDs have a strong advantage in terms of overcoming the size-dependent degradation of lLEDs.…”

“…163 Another route for improving the crystal quality of InGaN-based red LEDs is relaxing the strain. In 2023, Lim et al 67 reported that the growth of an In 0.3 Ga 0.7 N decomposition layer could effectively relax the strain. This high-indium-content In 0.3 Ga 0.7 N layer was decomposed during n-InGaN/n-GaN decomposition stop-layer (DSL) growth at 950 C, which generated tensile strain in the DSL layer.…”

“…Figure 16 summarizes the state-of-the-art red LEDs that have been reported in the last 6 years. The EQE is divided into three groups: AlGaInP LEDs (sky blue symbol), 68,80,86,151,153,180 InGaN LEDs emitting wavelengths over 625 nm (red symbol), 51,67,77,160,161,165,166,171,[181][182][183][184][185][186][187][188][189] and InGaN LEDs emitting wavelengths less 625 nm (green symbol). 66,163,168,169,188,[190][191][192][193][194][195][196][197][198][199] The EQE of the AlGaInP LEDs tends to decrease with a smaller size.…”

Recent Progress in Long‐Wavelength InGaN Light‐Emitting Diodes from the Perspective of Epitaxial Structure

“…[ 45 ] Using such relaxed InGaN buffer as pseudosubstrates, high‐indium‐composition QWs for red LEDs could be grown over a full 2 inch wafer at above 800 °C, representing a promising approach for red LEDs with long wavelength and high crystal quality at the same time. [ 46 ] Even et al investigated the effect of InGaN pseudosubstrate with varying a ‐lattice parameters (3.190, 3.200, 3.205 Å) on the emission characteristics of MQWs. [ 47 ] These pseudosubstrates were found to improve the indium incorporation rate due to the reduced compositional pulling effect caused by compressive strain.…”