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Tela Favaloro, Rajeev Singh, James Christofferson, Younes Ezzahri, Zhixi Bian, and Ali Shakouri

Tela Favaloro, Rajeev Singh, James Christofferson, Younes Ezzahri, Zhixi Bian, and Ali Shakouri Electrical Engineering Department, University of California, Santa Cruz, California 95064, USA Gehong Zeng, Je-Hyeong Bahk, and John E. Bowers

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Tela Favaloro, Rajeev Singh, James Christofferson, Younes Ezzahri, Zhixi Bian, and Ali Shakouri

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  1. Tela Favaloro, Rajeev Singh, James Christofferson, Younes Ezzahri, Zhixi Bian, and Ali Shakouri Electrical Engineering Department, University of California, Santa Cruz, California 95064, USA Gehong Zeng, Je-Hyeong Bahk, and John E. Bowers Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106, USA Hong Lu, and Arthur C. Gossard Materials Department, University of California, Santa Barbara, California 93106, US Transient Electrical and Thermal Characterization of InGaAlAs Thin Films with Embedded ErAs Nanoparticles

  2. Outline • High temperature apparatus for cross plane material characterization • Transient electrical measurements • Thermoreflectance imaging of thermoelectric devices in cooling and heating modes • Preliminary results ‘Merged’ Thermal Image -500ma, 550K ‘Merged’ Thermal Image +500mA, 550K

  3. 1 2 V24 I13 4 3 Thin Film Material Characterization Material Figure of Merit Established characterization techniques: • In-plane electrical conductivity and Seebeck (Van der Pauw, sample bars). • Need non-conducting substrate (difficult at high T). • Substrate transfer: stress issues • Cross-plane thermal conductivity • 3 (min ~0.5-1m; need electrical isolation between heater and thin film)‏ • Transient thermoreflectance (top 0.1-0.5 microns of the sample, frequency dependent issues)‏ x Also possible: Cross-plane determination of material parameters

  4. High Temperature Characterization System Sample mounted for thermal imaging Currently tested to vacuum of 10-6 mbar and temperatures above 800K High speed measurement stage

  5. Material System:Semimetal nanoparticles in semiconductor alloy • Thin film element: 50 m n-InGaAlAs, 0.6% ErAs • Substrate: 125 m AlN • Metal pad: 7 m Au • Mask: Dedicated voltage and current pads Mask design for cross-plane measurements

  6. Cross-Plane Transient Electrical Characterization 500 ns 750K 700K 300K 300K High speed circuitry enables below 100 nanosecond resolution

  7. Vsp (V)‏ 300K 500K 700K 120x120 μm2 560 1120 1690 70x70 μm2 798 1370 2110 Extraction of Joule and Peltier Voltages

  8. Thermoreflectance Imaging I=+95 mA I = -95 mA T=300K 50x50μm2 device in cooling mode 50x50μm2 device in heating mode 50x50μm2 device Subtracted Image for Peltier Cooling

  9. High Temperature Thermoreflectance Imaging T=700K I=- 95mA I =+95mA 50x50μm2 device in cooling mode 50x50μm2 device in heating mode 50x50μm2 device Subtracted image for Peltier Cooling

  10. Total Cooling Density Varies with Device Size Current injection nonuniformity and current spreading within the sample result in decreased ΔT in larger samples 50x50μm2 with 95mA excitation current 100x100μm2 with 140mA excitation current 150x150μm2 with 150mA excitation current ΔT=-3.995 ΔT=-2.067 ΔT=-1.655

  11. 300K 500K 700K Vsp (V)‏ 798 1370 2110 ΔT (K)‏ -4.215 -5.018 -6.656 Results and Conclusions Determination of Seebeck Coefficient for 70x70μm2 Sample: Measured change in temperature after subtraction of Joule heating at 100mA excitation:

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