Open AccessEffects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode
Author(s) -
Chih-Yen Chen,
Chieh Hsieh,
CheHao Liao,
W.F. Chung,
Hao-Tsung Chen,
Weixiao Cao,
Wen-Ming Chang,
Horng-Shyang Chen,
Yufeng Yao,
Shao-Ying Ting,
YeanWoei Kiang,
C. C. Yang,
Xiaocheng Hu
Publication year - 2012
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.20.011321
Subject(s) - materials science , photoluminescence , quantum well , light emitting diode , indium , optoelectronics , quantum confined stark effect , annealing (glass) , quantum efficiency , indium gallium nitride , diode , blueshift , wide bandgap semiconductor , optics , gallium nitride , layer (electronics) , nanotechnology , laser , composite material , physics
The counteraction between the increased carrier localization effect due to the change of composition nanostructure in the quantum wells (QWs), which is caused by the thermal annealing process, and the enhanced quantum-confined Stark effect in the QWs due to the increased piezoelectric field, which is caused by the increased p-type layer thickness, when the p-type layer is grown at a high temperature on the InGaN/GaN QWs of a high-indium light-emitting diode (LED) is demonstrated. Temperature- and excitation power-dependent photoluminescence (PL) measurements are performed on three groups of sample, including 1) the samples with both effects of thermal annealing and increased p-type thickness, 2) those only with the similar thermal annealing process, and 3) those with increased overgrowth thickness and minimized thermal annealing effect. From the comparisons of emission wavelength, internal quantum efficiency (IQE), spectral shift with increasing PL excitation level, and calibrated activation energy of carrier localization between various samples in the three groups, one can clearly see the individual effects of thermal annealing and increased p-type layer thickness. The counteraction leads to increased IQE and blue-shifted emission spectrum with increasing p-type thickness when the thickness is below a certain value (20-nm p-AlGaN plus 60-nm p-GaN under our growth conditions). Beyond this thickness, the IQE value decreases and the emission spectrum red shifts with increasing p-type thickness.