Internal Quantum Efficiency Enhancement of Deep-ultraviolet AlGaN Quantum Wells through Surface Plasmon Coupling with an Al Nano-grating Structure
Date Issued
2016
Date
2016
Author(s)
Chen, Wei-Han
Abstract
The enhancement of internal quantum efficiency (IQE) of deep-ultraviolet (UV) AlxGa1-xN/AlyGa1-yN (x < y) quantum wells (QWs) by fabricating one-dimensional Al nano-gratings on a QW structure for inducing surface plasmon (SP) coupling is demonstrated. Through temperature-dependent photoluminescence (PL) measurement, the enhancements of IQE in different emission polarizations are illustrated. Due to the small difference in energy band level between the heavy/light hole and split-off valence bands, the IQEs of the transverse-electric- (TE-) and transverse-magnetic- (TM-) polarized emissions are about the same. With SP coupling, the similar IQEs between different polarizations can also be attributed to the simultaneous SP couplings of the TE- and TM-polarized transitions. When emission polarization is perpendicular to Al-grating ridge, the SP resonance mode for coupling with the QWs is dominated by localized surface plasmon (LSP). When emission polarization is parallel with Al-grating ridge, the coupled-SP resonance mode mixes LSP and surface plasmon polariton. When the excitation laser polarization is perpendicular to Al-grating ridge, the strong LSP resonance at the excitation laser wavelength leads to stronger excitation and hence higher IQE levels. The IQE enhancement decreases with the distance between Al-grating ridge tip and the QWs.
Subjects
Surface Plasmon
Al Nano-grating Structure
AlGaN Quantum Wells
Deep-ultraviolet
Internal Quantum Efficiency
Type
thesis
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