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Scanning electron microscope as a flexible tool for investigating the properties of UV-emitting nitride semiconductor thin films

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Photonics Research 2019年第11期7卷 I0017-I0026页

作者： C.Trager-Cowan A.Alasmari W.Avis J.Bruckbauer P.R.Edwards B.Hourahine S.Kraeusel G.Kusch R.Johnston G.Naresh-Kumar R.W.martin m.Nouf-Allehiani E.Pascal L.Spasevski D.Thomson S.Vespucci P.J.Parbrook m.D.Smith J.Enslin F.mehnke m.kneissl C.Kuhn T.Wernicke S.Hagedorn A.Knauer V.Kueller S.Walde m.Weyers P.-m.Coulon P.A.Shields Y.Zhang L.Jiu Y.Gong R.m.Smith T.Wang A.Winkelmann Department of physics supauniversity of strathclydeglasgow G4 onguk Tyndall national institute university college corkcork t12 r5cpireland Institute of solid state physics lechnische universitat berlin10623 berlingermany Ferdinand-braun-lnstitut leibniz-lnstitut fur hochstfrequenztechnik12489 berlingermany Department of electronic and electrical engineering centre of nanoscience&nanotechnologyuniversity of bathbath ba27ayuk Department of electronic and electrical engineering university of sheffieldsheffield s13jduk Laser components department laser zentrum hannover 5.v.30419 hannovergermany

In this paper we describe the scanning electron microscopy techniques of electron backscatter diffraction, electron channeling contrast imaging, wavelength dispersive X-ray spectroscopy, and cathodoluminescence hyperspectral imaging. We present our recent results on the use of these non-destructive techniques to obtain information on the topography, crystal misorientation, defect distributions, composition, doping, and light emission from a range of UV-emitting nitride semiconductor structures. We aim to illustrate the developing capability of each of these techniques for understanding the properties of UV-emitting nitride semiconductors, and the benefits were appropriate, in combining the techniques.

关键词： electron nitride doping

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mOVPE-grown AlGaN-based tunnel heterojunctions enabling fully transparent UVC LEDs

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Photonics Research 2019年第5期7卷 I0008-I0012页

作者： Christian Kuhn Luca Sulmoni martin Guttmann Johannes Glaab Norman Susilo Tim Wernicke markus Weyers michael kneissl Technische Universitat Berlin Institute of Solid State Physics Hardenbergstr. 36 EW6-1 10623 Berlin Germany Ferdinand-Braun-Institut Leibniz-Institut fur Hochstfrequenztechnik Gustav-Kirchhoff-Str. 4 12489 Berlin Germany

We report on AlGaN-based tunnel heterojunctions grown by metalorganic vapor phase epitaxy enabling fully transparent UVC LEDs by eliminating the absorbing p-AlGaN and p-GaN layers. Furthermore, the electrical characteristics can be improved by exploiting the higher conductivity of n-AlGaN layers as well as a lower resistance of n-contacts. UVC LEDs with AlGaN:mg/AlGaN:Si tunnel junctions exhibiting single peak emission at268 nm have been realized, demonstrating effective carrier injection into the AlGaN multiple quantum well active region. The incorporation of a low band gap interlayer enables effective tunneling and strong voltage ***, the interlayer thickness is systematically varied. Tunnel heterojunction LEDs with an 8 nm thick GaN interlayer exhibit continuous-wave emission powers >3 m W near thermal rollover. External quantum efficiencies of 1.4% at a DC current of 5 m A and operating voltages of 20 V are measured on-wafer. Laterally homogeneous emission is demonstrated by UV-sensitive electroluminescence microscopy images. The complete UVC LED heterostructure is grown in a single epitaxy process including in situ activation of the magnesium acceptors.

关键词： mOVPE-grown AlGaN-based UVC LEDs

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Current-induced degradation and lifetime prediction of 310 nm ultraviolet light-emitting diodes

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Photonics Research 2019年第7期7卷 14-18页

作者： Jan Ruschel Johannes Glaab Batoul Beidoun Neysha Lobo Ploch Jens Rass Tim Kolbe Arne Knauer markus Weyers Sven Einfeldt michael kneissl Ferdinand-Braun-Institut Leibniz-Institut fur HochstfrequenztechnikGustav-Kirchhoff-Str.412489 BerlinGermany Technische Universitat Berlin Institut fur FestkorperphysikHardenbergstr.36EW6-710623 BerlinGermany

The impact of operation current on the degradation behavior of 310 nm UV LEDs is investigated over 1000 h of stress. It ranges from 50 to 300 mA and corresponds to current densities from 34 to 201 A/cm^*** separate the impact of current from that of temperature, the junction temperature is kept constant by adjusting the heat sink temperature. Higher current was found to strongly accelerate the optical power reduction during operation. A mathematical model for lifetime prediction is *** indicates that lifetime is inversely proportional to the cube of the current density, suggesting the involvement of Auger recombinati on.

关键词： degradation light-emitting diodes lifetime

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Displacement Talbot lithography for nanoengineering of III-nitride materials

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microsystems & Nanoengineering 2019年第1期5卷 38-49页

作者： Pierre-marie Coulon Benjamin Damilano Blandine Alloing Pierre Chausse Sebastian Walde Johannes Enslin Robert Armstrong Stephane Vezian Sylvia Hagedorn Tim Wernicke Jean massies Jesus Zuniga‐Perez markus Weyers michael kneissl Philip A.Shields Department of Electrical&Electronic Engineering University of BathBath BA27AYUK Universite Cote d’Azur CNRSCRHEArue B.Gregory06560 ValbonneFrance Ferdinand-Braun-Institut Leibniz-Institut fur HochstfrequenztechnikGustav-Kirchhoff-Str.412489 BerlinGermany Technische Universität Berlin Institute of Solid State Physics10623 BerlinGermany

Nano-engineering III-nitride semiconductors offers a route to further control the optoelectronic properties,enabling novel functionalities and *** a variety of lithography techniques are currently employed to nanoengineer these materials,the scalability and cost of the fabrication process can be an obstacle for large-scale *** this paper,we report on the use of a fast,robust and flexible emerging patterning technique called Displacement Talbot lithography(DTL),to successfully nano-engineer III-nitride ***,along with its novel and unique combination with a lateral planar displacement(D^(2)TL),allow the fabrication of a variety of periodic nanopatterns with a broad range of filling factors such as nanoholes,nanodots,nanorings and nanolines;all these features being achievable from one single *** illustrate the enormous possibilities opened by DTL/D2TL,dielectric and metal masks with a number of nanopatterns have been generated,allowing for the selective area growth of InGaN/GaN core-shell nanorods,the top-down plasma etching of III-nitride nanostructures,the top-down sublimation of GaN nanostructures,the hybrid top-down/bottom-up growth of AlN nanorods and GaN nanotubes,and the fabrication of nanopatterned sapphire substrates for AlN *** with their planar counterparts,these 3D nanostructures enable the reduction or filtering of structural defects and/or the enhancement of the light extraction,therefore improving the efficiency of the final *** results,achieved on a wafer scale via DTL and upscalable to larger surfaces,have the potential to unlock the manufacturing of nano-engineered III-nitride materials.

关键词： Talbot planar nitride

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