Gallium Nitride

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Gallium Nitride. Research & Development. Presented by Rakesh Sohal Supervision Prof. Dieter Schmeißer. GaN - Research & Development. Outline. Introduction GaN - Physics Crystal Growth MOVPE MBE Substrates & Buffer layers Recent Advances Applications. - PowerPoint PPT Presentation

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  • Gallium NitridePresented by

    Rakesh Sohal

    SupervisionProf. Dieter SchmeierResearch & Development

  • OutlineIntroductionGaN - PhysicsCrystal Growth MOVPE MBESubstrates & Buffer layersRecent AdvancesApplicationsGaN - Research & Development

  • Why GaN ?Semiconductor with Direct and Wide BandgapOptoelectronics DevicesBlue & Blue/green light emittersTransistors withstand extreme heat andHigh frequencies and power levelsMore efficient amplifiers at base stationsSi-only 10% power used and 90% wasted as heatGaN - Research & Development

  • GaN PhysicsCrystal StructureZince BlendeWurtziteGaN - Research & Development

  • GaN PhysicsEnergy band StructureGaN - Research & Development

  • GaN comparisonSilicon cannot provide the power-bandwidth product for military applicationsGaN - Research & Development

  • GaN-Crystal GrowthFirst epilayer by vapour transport - Murusk and Tietjen (1969) Growth rate - 0.5m/min. High background n-type carrier concentrations ~1019 cm-3

    Modern Technique - MOVPE by Nakamura Key aspect : downward subflow of He and N2 Claim - Improves the interaction of the reactant gases with the substrate

    Shortcomings High Substrate temperature Thermal mismatch strain & defectsMOVPE ApproachGaN - Research & Development

  • GaN-Crystal GrowthMBE ApproachN - supplied by -wave plasma excitation provided by compact ECR Limited N-flux lower growth rate(GR) ~ 500/hr.

    GR can be increased by higher power Degraded Material QualityGaN - Research & Development

  • GaN-Crystal GrowthSubstrates for EpigrowthBaule Growth efforts are ongoingTill date - not possible

    The only Option - HeteroepitaxyThe most Stringent Issue/BarrierGaN - Research & Development

  • GaN-Crystal GrowthSubstrates for EpigrowthThermal & lattice mismatch - Strain and DefectsGaN - Research & Development

  • GaN-Crystal GrowthSubstrates for EpigrowthThermal & lattice mismatch - Strain and DefectsGaN - Research & Development

  • GaN - Research & DevelopmentGaN-Crystal GrowthInterfacial buffer layer

  • GaN-AdvancesThree major hurdles has been clearedHeteroepitaxy - via buffer layerControl of n (Si) & p(Mg)-type dopingReduction in dislocation densityResidual e-concentrations - --- due to N-vacancies(earlier) Van de Walle showed - energy required for Nv too high--- due to O incorporationGaN - Research & Development

  • GaN-AdvancesUse for patterned SiO2Robert F. Davis, Proceedings of the IEEE, Vol. 90, No. 6, 2002GaN - Research & Development

  • Comparison - bulbs & LEDsGaN - Research & Development

  • New two flow MOCVDNakamuras MethodGaN - Research & Development

  • Pioneer of Nakamura 1989-Started III-V nitride research.1990-Develops new two-flow MOCVD equipment for growth of high quality single crystal GaN layers.1992-begins to grow InGaN single crystal layers for the production of double heterostructures.1993-Succeeded in developing a blue LED with a luminous intensity as high as 2cd using III-V nitride materials.1995-Developed high-brightness SQW structure blue/green LEDs with a luminous intensity of 2 cd and 10 cd, and developed a violet laser diode using III-V nitride materials for the first time.1996-The first current infection III-V nitride based LDs were fabricated.1996-Announces the first CW blue GaN based injection laser at room temperature.GaN - Research & Development

  • The thickness of the GaN buffer layer was varied between 100 and 1200 The substrate was heated to 1050oC in a stream of hydrogenThe substrate temperature was elevated to between 1000oC and 1030oC to grow the GaN film.The substrate temperature was lowered to between 450oC and 600oC to grow the GaN buffer layer.The total thickness of the GaN film was about 4 mm,and the growth time was 60 min.Steps to grow crystalline GaNNakamuras MethodGaN - Research & Development

  • Buffer layer thicknessThe value of the FWHM is almost constant between 200 and 1200 thickness.The optimum thickness of the GaN buffer layer was around 200 GaN - Research & Development

  • GAN - PotentialGaN - Research & Development

  • Large scale displays (large outdoor television screens)Smaller full-color flat panel display screens(inside trains or subway stations)Full-color scannersFull-color photocopying machinesFull-color FAX machinesTraffic lightsLED white lampsApplicationsGaN - Research & Development

  • Applications2 inch dia blue LED wafer on GaN-on-sapphireGaN - Research & Development

  • Thanks for your attention!GaN - Research & Development