Significant increase of quantum efficiency of green InGaN quantum well by realizing step-flow growth

Abstract

Two-dimensional (2D) island morphologies have been widely reported for green light-emitting InGaN quantum well (QW) layers, but the step-flow morphology has not been obtained for a green InGaN QW layer to date. In this Letter, we first investigate the cause of the 2D island morphology of green InGaN QWs via a comparison study with blue InGaN QWs. The short diffusion lengths of adatoms at low growth temperatures were found to be the cause of the 2D island morphology for the green InGaN QW. Step-flow growth of green InGaN QWs was obtained by increasing the miscut angle of the c-plane GaN substrates from 0.20° to 0.48°, which reduces the atomic terrace width. Green InGaN/GaN multiple quantum wells (MQWs) with step-flow morphologies were found to have sharper well/barrier interfaces than MQWs with 2D island morphologies. The internal quantum efficiency of the green InGaN/GaN MQWs with the step-flow morphology is double that of the corresponding MQWs with the 2D island morphology at an excitation power density of 6.4 kW/cm2. Additionally, the emission linewidth of the green InGaN/GaN MQWs with the step-flow morphology is greatly reduced. As a result, the threshold currents of green laser diodes with larger miscut angles are greatly reduced.

Significant improvement of green light emission efficiency of InGaN/GaN quantum wells by depositing oxide thin films and ultraviolet light irradiations

“…Regarding the rate of increase in IQE in the green region, its value increases at an unparalleled rate 29 -33 . Figure 4a shows the IQE obtained in this study and those of other groups reported recently [23][24][25][26] . The improved IQE of SQW and 3QW are plotted as blue, green, and red stars, respectively.…”

InGaN Platelets: Synthesis and Applications toward Green and Red Light-Emitting Diodes

“…19,20 Until now, the growth of thick InGaN layers has not been extensively studied because of the synthesis challenges arising from the phase separation and surface control. 21,22 Pantzas et al reported that insertions of thin GaN interlayers during InGaN growth can suppress the phase separation and improve the surface quality. However, the reported root-mean-square roughness of 3.1 nm still seems too high for the subsequent QW growth.…”

“…A reduced QCSE leads to an increased overlap between electron and hole wave functions, and a much higher spontaneous emission rate can be achieved compared to the same InGaN QWs grown on a GaN buffer layer. , Even et al studied the growth dependence of InGaN QWs on the indium content in InGaN pseudosubstrates and found an enhanced indium incorporation into the QWs due to the reduced indium pulling effect . This enables the growth of green and red InGaN QWs at a higher temperature for a higher quality. , In addition, a higher hole concentration is expected in InGaN as a result of a lower activation energy for the p-type doping compared to GaN. , Until now, the growth of thick InGaN layers has not been extensively studied because of the synthesis challenges arising from the phase separation and surface control. , Pantzas et al reported that insertions of thin GaN interlayers during InGaN growth can suppress the phase separation and improve the surface quality. However, the reported root-mean-square roughness of 3.1 nm still seems too high for the subsequent QW growth .…”

Carrier Recombination in Nitride-Based Light-Emitting Devices: Multiphonon Processes, Excited Defects, and Disordered Heterointerfaces

“…Both NAs and RAFs manifest themselves in features of the surface morphology [14,15]. According to [13,16], these features are characterized by the degree of nanomaterial disorder (DND). So, in further discussion regarding DND, we will understand it as the nanoarrangement of domain structure, RAFs, and the presence of local regions with disrupted stoichiometry of alloy composition.…”