Group Meeting Research Update (10-5-2012)

Brongersma group meeting research update presentation

Transcript

1. When semiconductors go Metal Alok Vasudev group meeting 10/2/12
3. Not quite this metal
4. That’s about right = 2 p 2 + ı
5. Band transitions dominate semiconductor optics
6. Band transitions dominate semiconductor optics B2B LED, Photodiode
7. Band transitions dominate semiconductor optics B2B LED, Photodiode QW B2B Laser, Modulator
8. Band transitions dominate semiconductor optics B2B LED, Photodiode QW B2B Laser, Modulator QW ISB QCL
9. A Drude model describes the optical response of free electrons = 1 2 p 2 n e2 0 m
10. A corrected Drude model describes real metals = 2 p 2 + ı contribution of the bound electrons electron scattering
11. A corrected Drude model describes real metals 10 0 10 _2{ }
12. A corrected Drude model describes real metals 10 0 10 _2{ } epsilon near zero
13. A corrected Drude model describes real metals 10 0 10 _2{ } epsilon near zero plasmonic
14. Today’s takeaways • Semiconductors in the “free- electron regime” offer intriguing possibilities • ENZ materials can modulate silicon waveguide modes • Degenerately doped III-Vs are good mid-IR plasmonic materials
15. Silicon waveguide modulation with an ENZ region
16. ENZ materials present a unique BC on normal electric fields En1 En2 = 2 1 1 2
17. ENZ materials present a unique BC on normal electric fields En1 En2 = 2 1 1 2 En1 En2 b 1 0
18. We can exploit this effect for optical modulation
19. We can exploit this effect for optical modulation Si 0 < < 12
20. We can exploit this effect for optical modulation Si 0 < < 12 ON
21. We can exploit this effect for optical modulation Si 0 < < 12 Si 0 ON
22. We can exploit this effect for optical modulation Si 0 < < 12 Si 0 ON OFF
23. We can exploit this effect for optical modulation Si 0 < < 12 Si 0 ON OFF We need a material we can switch from dielectric to ENZ on-demand
24. −12 −10 −8 −6 −4 −2 1 1.00 1.30 1.55 1.70 2.00 Wavelength [µm] −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 2 Accumulating electrons in ITO allows on-demand ENZ creation −12 −10 −8 −6 −4 −2 0 2 4 1 1.5 2.0 2.5 3.0 2 _2{ } [µK] n = 1×1019 cm-3 1.4×1021 6.3×1020
25. −12 −10 −8 −6 −4 −2 1 1.00 1.30 1.55 1.70 2.00 Wavelength [µm] −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 2 Accumulating electrons in ITO allows on-demand ENZ creation −12 −10 −8 −6 −4 −2 0 2 4 1 1.5 2.0 2.5 3.0 2 _2{ } [µK] n = 1×1019 cm-3 1.4×1021 6.3×1020
26. −12 −10 −8 −6 −4 −2 1 1.00 1.30 1.55 1.70 2.00 Wavelength [µm] −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 2 Accumulating electrons in ITO allows on-demand ENZ creation −12 −10 −8 −6 −4 −2 0 2 4 1 1.5 2.0 2.5 3.0 2 _2{ } [µK] n = 1×1019 cm-3 1.4×1021 6.3×1020 * assuming 5 nm HfO2 gate dielectric V = 0 V V = 5 V
27. A coated Si waveguide forms an MOS capacitor SiO2 Si
28. Si Si 10 nm ITO 5 nm HfO2 A coated Si waveguide forms an MOS capacitor SiO2 Si
29. Si Si This waveguide supports two modes SiO2 Si 10 nm ITO 5 nm HfO2
30. Si Si This waveguide supports two modes SiO2 Si 10 nm ITO 5 nm HfO2 Ex | n 1016 1019 1016 1019 Ex | TM0 TE1 TM0 |Ex |
31. Si Si This waveguide supports two modes SiO2 Si 10 nm ITO 5 nm HfO2 Ex | n 1016 1019 1016 1019 Ex | TM0 TE1 TM0 |Ex | 016 019 1016 1019 |E |E TM0 TE1 TE1 |Ey |
32. Si Si This waveguide supports two modes SiO2 Si 10 nm ITO 5 nm HfO2 Ex | n 1016 1019 1016 1019 Ex | TM0 TE1 TM0 |Ex | 016 019 1016 1019 |E |E TM0 TE1 TE1 |Ey |
33. This modulator operates via electro-absorption −12 −10 −8 −6 −4 −2 0 2 4 1 1.00 1.30 1.55 1.70 2.00 Wavelength [µm] −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 2 _2{ } [µK] AK{ } accumulating electrons accumulating electrons
34. This modulator operates via electro-absorption −12 −10 −8 −6 −4 −2 0 2 4 1 1.00 1.30 1.55 1.70 2.00 Wavelength [µm] −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 2 _2{ } [µK] AK{ } accumulating electrons accumulating electrons
35. This modulator operates via electro-absorption −12 −10 −8 −6 −4 −2 0 2 4 1 1.00 1.30 1.55 1.70 2.00 Wavelength [µm] −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 2 _2{ } [µK] AK{ } accumulating electrons accumulating electrons AK{ } b _2{ }
36. This modulator operates via electro-absorption −12 −10 −8 −6 −4 −2 0 2 4 1 1.00 1.30 1.55 1.70 2.00 Wavelength [µm] −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 2 _2{ } [µK] AK{ } accumulating electrons accumulating electrons AK{ } b _2{ } Nothing new! Same thing in Si
37. This modulator operates via electro-absorption −12 −10 −8 −6 −4 −2 0 2 4 1 1.00 1.30 1.55 1.70 2.00 Wavelength [µm] −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 2 _2{ } [µK] AK{ } accumulating electrons accumulating electrons AK{ } b _2{ } Nothing new! Same thing in Si But ENZ enhances field precisely in absorbing region
38. This modulator operates via electro-absorption −12 −10 −8 −6 −4 −2 0 2 4 1 1.00 1.30 1.55 1.70 2.00 Wavelength [µm] −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 2 _2{ } [µK] AK{ } accumulating electrons accumulating electrons AK{ } b _2{ } Nothing new! Same thing in Si But ENZ enhances field precisely in absorbing region No field enhancement in Si
39. High electric fields correspond to ENZ regions | 1016 1019 1016 1019 TM0 TE1 |Ex | ON |Ex | n 1016 1019 1016 1019 6.33×1020 |Ex | n ON OFF |Ex | OFF ENZ ITO accumulation regions
40. 3 dB modulation depth in under 30 microns 0 5 10 15 20 25 30 Length [µm] −4.0 −3.5 −3.0 −2.5 −2.0 −1.5 −1.0 −0.5 0.0 Loss [dB] TE1 (ON) TM0 (ON) TE1 (OFF) TM0 (OFF)
41. Mid-IR plasmonics with degenerately-doped semiconductors
42. Mid-IR plasmonics: (relatively) uncharted territory Mid-infrared spectrum hosts a variety of intriguing phenomena
43. Mid-IR plasmonics: (relatively) uncharted territory Mid-infrared spectrum hosts a variety of intriguing phenomena Perhaps surface plasmons can play a role?
44. Epitaxial semiconductors and semimetals span the mid-IR Reflectance Wavelength [microns] ErAs LuAs InAs (2 dopings)
45. InAs is a promising mid-IR plasmonic material • Supports doping ~1020 cm-3 • Small effective mass
46. InAs is a promising mid-IR plasmonic material • Supports doping ~1020 cm-3 • Small effective mass 2 p = n e2 0m
47. InAs is a promising mid-IR plasmonic material • Supports doping ~1020 cm-3 • Small effective mass 2 p = n e2 0m • Compatible with GaAs family
48. InAs is a promising mid-IR plasmonic material • Supports doping ~1020 cm-3 • Small effective mass 2 p = n e2 0m We need to measure SPPs in InAs • Compatible with GaAs family
49. Attenuated total reflectance allows direct excitation of SPPs An ev LQWHUQ H[FLWH $GLS VSRQ 7KHD PLQH 7KHZ GLSF W0DGGR[0DUN/%URQJHUVPD6HWK5% VXUIDFHSODVPRQFRXSOLQJYLDDQ2WW " JK U W- DWH- DOV S- DQG )7Ζ5 0&7 Ɩ 1 FFT SULVP semiconductor VSS UHȵHFWDQFH DLUJDS Ɩ k SULVPOLJKWOLQH VSSGLVSHUVLRQ
50. Doping affects the ATR dip location More doping Attenuated total reflectance Wavelength [microns] ~1020 cm-3 ~1018 cm-3
51. Air gap-dependence confirms SPP coupling 6 7 8 9 10 40 50 60 70 80 90 100 110 Attenuated total reflectance Wavelength [microns] shrinking air gap
52. ATR lets us use SPPs to characterize InAs •Dopant activation •Effective mass •Scattering time We can now measure
53. We can also derive the optical properties of InAs 100 80 60 40 20 0 20 1000 2000 3000 4000 5000 6000 0 1 2 3 4 5 6 7 8 9 _2{ } AK{ } Wavenumbers [1/cm]