Browsing by Author "Sun, Qian"

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Effect of Controlled Growth Dynamics on the Microstructure of Nonpolar a-Plane GaN Revealed by X-ray Diffraction
(2009-07-01)
Sun, Qian
;
Ko, Tsung-Shine
;
Yerino, Christopher D.
;
Zhang, Yu
;
Lee, In-Hwan
This paper reports the effect of controlled growth dynamics, as monitored by in situ optical reflectance, on the microstructure of nonpolar a-plane GaN films grown on r-plane sapphire. The mosaic microstructure of a-plane GaN and its anisotropy are evaluated by X-ray rocking curve (XRC) measurements. By inserting a pronounced islanding stage followed by an enhanced lateral growth, pit-free a-plane GaN has been achieved showing an XRC linewidth of similar to 0.18 and similar to 0.3 degrees for on- and off-axes planes, respectively, with only minor anisotropy. The density of basal-plane stacking faults is reduced by similar to 70% as determined by a modified Williamson-Hall X-ray analysis. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/JJAP.48.071002
Effects of thickness on optical characteristics and strain distribution of thin-film GaN light-emitting diodes transferred to Si substrates
(2016-04)
Li, Heng
;
Shi, Yang-Da
;
Feng, Meixin
;
Sun, Qian
;
Lu, Tien-Chang
We investigated the effect of device thickness on the internal quantum efficiency (IQE) of thin-film GaN light-emitting diodes (LEDs), which were grown on Si substrates and transferred to other Si substrates with reduced film thickness. It was confirmed by Raman spectroscopy and photoluminescence measurement that the compressive strain is released and the quantum-confined Stark effect (QCSE) is suppressed after reducing the thickness. The best IQE of 62.9% was reached with a large suppression of the band tilting by QCSE, from 7.9meV in the original structure to 2.4meV in the thinnest sample, and this value can compete with that of GaN-based LEDs grown on a sapphire substrate. (C) 2016 The Japan Society of Applied Physics
UVA light-emitting diode grown on Si substrate with enhanced electron and hole injections
(2017-11-01)
Zhang, Zi-Hui
;
Chu, Chunshuang
;
Chiu, Ching Hsueh
;
Lu, Tien Chang
;
Li, Luping
In this work, III-nitride based similar to 370 nm UVA lightemitting diodes (LEDs) grown on Si substrates are demonstrated. We also reveal the impact of the AlN composition in the AlGaN quantum barrier on the carrier injection for the studied LEDs. We find that, by properly increasing the AlN composition, both the electron and hole concentrations in the multiple quantum wells (MQWs) are enhanced. We attribute the increased electron concentration to the better electron confinement within the MQW region when increasing the AlN composition for the AlGaN barrier. The improved hole concentration in the MQW region is ascribed to the reduced hole blocking effect by the p-type electron blocking layer (p-EBL). This is enabled by the reduced density of the polarization-induced positive charges at the AlGaN last quantum barrier (LB)/p-EBL interface, which correspondingly suppresses the hole depletion at the AlGaN LB/p-EBL interface and decreases the valence band barrier height for the p-EBL. As a result, the optical power is improved. (C) 2017 Optical Society of America