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Published byAbner Little Modified over 9 years ago
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Results and discussion
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Conclusion In conclusion, thinning the sapphire substrate enables the control of the residual compressive stress developed in the GaN-based near-UV LEDs by changing the curvature of the wafer bowing. The wafer bowing-induced mechanical stress alters the piezoelectric fields, which in turn reduces the QCSE in the InGaN/GaN MQW active region. The reduction in piezoelectric fields causes a blue-shift in EL spectra, an increase in IQE, and improvement of the light output power. In addition, EQE and WPE were optimized because of the enhanced light output intensity.
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Conclusion The results confirmed that the reduction in the piezoelectric field due to stress relaxation by thinning the sapphire substrate thickness in the InGaN/GaN MQWs caused an enlargement of the effective band gap, and an increase in both the electron–hole wave function overlap and the probability of radiative recombination, along with a corresponding increase in IQE. The simulation results are in a good agreement with the experimental data.
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