1 / 11

F.Bertram et al. Material Science and Engineering B93 (2002) 19-23

Spatial variation of luminescence of InGaN alloys measured by highly-spatially-resolved scanning cathodoluminescence. F.Bertram et al. Material Science and Engineering B93 (2002) 19-23. Itoh Lab. Takahiro Doki. Contents. ・ Introduction -InGaN -Cathodoluminescence ・ Motivation

bailey
Download Presentation

F.Bertram et al. Material Science and Engineering B93 (2002) 19-23

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Spatial variation of luminescence of InGaN alloys measured by highly-spatially-resolved scanning cathodoluminescence F.Bertram et al. Material Science and Engineering B93 (2002) 19-23 Itoh Lab. Takahiro Doki

  2. Contents ・Introduction -InGaN -Cathodoluminescence ・Motivation ・Sample ・Experimental Results ・Summary

  3. InGaN Ultraviolet laser diodes (LD) Blue light-emitting diodes (LED) Green (http://www.marumet.co.jp/closeup/led.htm ) ( InN )x + ( GaN )1- x = (Eg~0.80 eV)(Eg~3.40 eV) InxGa1-xN Bandgap energy of InxGa1-xN EInGaN(x) = xEInN + (1-x)EGaN –bx(1-x) b: bowing parameter EInN = 0.80(eV), EGaN= 3.40(eV) b= 2.0(eV)

  4. Effective localization of carriers in Indium-rich potential minima InGaN Nonradiative High quantum efficiency despite high defect densities Thermal Exciton Potential Energy Lattice defect In-rich Radiative Position

  5. Electron beam Auger electron Secondary electron Cathodoluminescence （CL） Ｘ-ray Sample High spatial resolution Cathodoluminescence ・Cathodoluminescence (CL) ：Luminescence under electron beam irradiation Wavelength of an electron beam is very short. Small excitation spot (to ~10nm) ・Secondary electron 　→Observation of an image by the scanning electron microscope (SEM)

  6. Motivation • It is said that strong localization of carriers due to inhomogeneity of In concentration results in the high quantum efficiency. • The structural dependence of optical properties of InGaN have been extensively investigated by CL, Micro-PL and SNOM. SNOM: Scanning Near Field Optical Microscope CL measurement to reveal a correlation of microstructures with luminescence for InGaN

  7. 30nm InGaN 100nm 20nm 4μm 10nm Buffer layer 0nm Substrate GaN AlGaN sapphire Sample InxGa1-xN (x= 0.03-0.20) AFM image (x = 0.17) AFM: Atomic Force Microscope

  8. Experimental Results ① CL overview spectra (a, d) & The images of emission peaks (b, e) InxGa1-xN x=0.03 Main peak Narrow spectral range Single peak Main peak x=0.17 Additional peaks Wide spectral range First peak Second peak x> 0.1

  9. 3nm Experimental Results　② SEM image of InGaN sample with x=0.13. Spike Plateau Crater Craters (density of 2.9 × 108 cm-2) Spikes (density of 1.9 × 107 cm-2)

  10. Experimental Results　③ Images of CLI in the main peak(430nm), the first(450nm), second peak(468nm) of CL overview spectra from InGaN sample with x=0.13. 430nm(Main peak) 468nm(Second peak) 450nm(First peak) Almost homogeneous Exclusively from craters and spikes

  11. Summary • Highly-spatially-resolved cathodoluminescence was measured for InGaN alloys. • The samples with the low In concentration show one main peak in CL spectra. • The sample with the high In concentration has many nanostructures of craters and spikes. CL spectrum shows a main peak originating from all the area and the additional peaks at the lower energy side originating from the nanostructures. • As a result, it was suggested that craters and spikes has In-rich composition and the carriers are strongly localized at them.

More Related