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We have successfully fabricated 7-μm 155-nm-thick undercut microdisk cavities with AlN / Al0.60Ga0.40N (5.5 nm / 2.5 nm) multiple quantum wells epitaxially grown on Si substrate by metal–organic chemical vapor deposition. Upon optical pumping, whispering-gallery modes (WGMs) with wavelengths around ∼250 nm can be observed throughout the photoluminescence spectrum at room temperature, with quality factors around 500 to 1000. These cavity modes have been analyzed by theoretical calculations. Our results suggest great potentials to demonstrate WGM lasing in the UVC range from these AlGaN/AlN-on-Si microdisk cavities monolithically grown on a Si platform.
This work reports AlGaN-based deep ultraviolet light-emitting diode (DUV LED) possessing a specifically AlxGa1 − xN / AlyGa1 − yN / AlxGa1 − xN (x > y) structured p-electron blocking layer (p-EBL) to achieve the high external quantum efficiency (EQE). The impact of the p-EBL with AlyGa1 − yN insertion layer at different positions and with different AlN compositions on the hole and electron injection is systematically investigated. Our results show that, for the DUV LED structure in this work, both electrons and holes can be most efficiently injected into the active region by keeping the AlyGa1 − yN insertion layer near to the p-region. The AlN composition for the AlyGa1 − yN insertion layer has also to be optimized for maximizing the carrier injection.
In recent decades, literatures about visible vertical cavity surface emitting lasers (VCSELs) have been reported. However, due to high optical loss in the cavity, lasing from deep ultraviolet (DUV) VCSEL was still rarely achieved. The optical loss in nitride DUV microcavity was analyzed in detail. DUV nitride vertical Fabry–Pérot microcavity with active layer of AlGaN-based quantum dots and double-side HfO2 / SiO2 distributed bragger reflectors was fabricated. Optical losses with of the order of 103 cm − 1 were deduced from the Q value of the cavity modes. The main origination of optical loss in DUV cavity was calculated and ascribed to the interface scattering. The interface roughness appearing after laser lift-off process and overlap between rough interface and standing optical wave were two key parameters that contributed to interface scattering loss. We believe that our results will provide useful information for improving DUV VCSEL devices.