6 research outputs found
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Improving AlN Crystal Quality and Strain Management on Nanopatterned Sapphire Substrates by High-Temperature Annealing for UVC Light-Emitting Diodes
Herein, AlN growth by metalorganic vapor-phase epitaxy on hole-type nanopatterned sapphire substrates is investigated. Cracking occurs for an unexpectedly thin-layer thickness, which is associated to altered nucleation conditions caused by the sapphire pattern. To overcome the obstacle of cracking and at the same time to decrease the threading dislocation density by an order of magnitude, high-temperature annealing (HTA) of a 300 nm-thick AlN starting layer is successfully introduced. By this method, 800 nm-thick, fully coalesced and crack-free AlN is grown on 2 in. nanopatterned sapphire wafers. The usability of such templates as basis for UVC light-emitting diodes (LEDs) is furthermore proved by subsequent growth of an UVC-LED heterostructure with single peak emission at 265 nm. Prerequisites for the enhancement of the light extraction efficiency by hole-type nanopatterned sapphire substrates are discussed. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
Improving AlN Crystal Quality and Strain Management on Nanopatterned Sapphire Substrates by HighâTemperature Annealing for UVC LightâEmitting Diodes
Herein, AlN growth by metalorganic vaporâphase epitaxy on holeâtype nanopatterned sapphire substrates is investigated. Cracking occurs for an unexpectedly thinâlayer thickness, which is associated to altered nucleation conditions caused by the sapphire pattern. To overcome the obstacle of cracking and at the same time to decrease the threading dislocation density by an order of magnitude, highâtemperature annealing (HTA) of a 300ânmâthick AlN starting layer is successfully introduced. By this method, 800ânmâthick, fully coalesced and crackâfree AlN is grown on 2âin. nanopatterned sapphire wafers. The usability of such templates as basis for UVC lightâemitting diodes (LEDs) is furthermore proved by subsequent growth of an UVCâLED heterostructure with single peak emission at 265ânm. Prerequisites for the enhancement of the light extraction efficiency by holeâtype nanopatterned sapphire substrates are discussed.BMBF, 03ZZ0134B, Zwanzig20 - Advanced UV for Life - Verbundvorhaben: UV Power; TP2: Entwicklung von high-power UVB-LEDs um 300 nmDFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement
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