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Results and discussion
Results and discussion
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.
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.