Silicon Photonics Photo-Detector Announcement Mario Paniccia Intel Fellow Director, Photonics Technology Lab
Agenda Intel s Silicon Photonics Research 40G Modulator Recap 40G Photodetector Announcement Vision of Future Terascale Platforms Summary 2
Photonics: The technology of emission, transmission, control and detection of light (photons) aka fiberoptics & opto-electronics Today: Most photonic devices made with exotic materials, expensive processing, complex packaging Silicon Photonics Vision: Research effort to develop photonic devices using silicon as base material and do this using standard, high volume silicon manufacturing techniques in existing fabs Benefit: Bring volume economics to optical communications 3
Intel s Silicon Photonics Research Continuous Wave Silicon Raman Laser (Feb 05) Electrically Pumped Hybrid Silicon laser (September 2006) 40 Gb/s TODAY 1GHz ( Feb 04) 1GHz 10 Gb/s (Apr (Apr 05) 40 Gb/s (Jul 07) Achieved 40 Gb/s for most devices Next: Focus on integration 4
40Gb/s Silicon Laser Modulator Encodes data on a light beam at 40Gbps Fastest Si modulator on par with fastest modulators available commercially 5
Guiding Light Communications Intel Litho transistor Silicon Silicon oxide oxide Ex: Rib waveguide Silicon Bandgap is Transparent to infra Red light (λ>1.1um) Can guide light in Silicon But does not absorb/detect 6
How do we absorb light: Use Germanium Bandgap engineering i.e. add another material Ge is the most promising candidate: High absorption for wavelengths of interest CMOS compatible Silicon Silicon Germanium oxide oxide Ex: Rib waveguide bigger is better 7
Challenge: Strain Crystal structure of germanium is 4% larger than silicon. This introduces strain when Ge is grown on Si. Result crystal lattice dislocations excess noise Bulk Films of Si and Ge Strained Si 1-x Ge x on Si Relaxed Si 1-x Ge x on Si a Ge ~.565 nm a Si ~.543 nm misfit dislocation Misfit dislocations typically create threading dislocations which h degrade device performance - dark current (I( dk ) goes up. By optimizing the thermal growth process parameters we can minimize defects impact. 8
Photodetector Design SEM Cross-Section N-Ge i-ge P-contact P-contact Si Si SiO SiO 2 2 (BOX) Si Si (Substrate) Passivation N-contact Ge Ge Rib Rib waveguide P-contact P-contact 9
World s best Waveguide Photodetector Performance Performance combines Speed = bits per second Efficiency = % of photons detected Noise = dark current ) Results: 40 Gb/s operation 95% efficient (up to λ ~1.56um) < 200nA of dark current 10
Experimental Results: Normalized response (db) 3 0-3 -6-9 ~ 31 GHz roll-off 1G 1 10G Frequency (GHz) 31 GHz Optical Bandwidth 40 Gb/s Data transmission World s Best Performing Ge Waveguide Photodetector 11
Tera-leap to Parallelism: ENERGY-EFFICIENT PERFORMANCE Hyper-Threading Instruction level parallelism Dual Core 10 s to 100 s of cores Quad-Core The days of single-core chips Era of Tera-Scale Computing More performance Using less energy TIME All this compute capability may require high speed optical links 12
Future Physical I/O for a Tera-scale Servers Core-Core: Core: On Die Interconnect fabric Memory: Package 3D Stacking Chip-Chip: Chip: Fast Copper FR4 or Flex cables Memory Memory Tb/s of I/O Tera-scale CPU Memory CPU 2 Memory Integrated Tb/s Optical Chip 13
Silicon Photonics for Computing Future: A Terabit Optical Chip Optical Fiber Multiplexor 25 modulators at 40Gb/s 25 hybrid lasers A future integrated terabit per second optical link on a single chip 14
Silicon Photonics for Computing Integrating into a Tera-scale System This transmitter would be combined with a receiver Rx Tx Which could then be built into an integrated, silicon photonic chip 15
Silicon Photonics for Computing Integrating into a Tera-scale System This integrated silicon photonic chip could then be integrated And this board could be into computer boards integrated into a Tera- scale system Integration of photonic devices will be critical in future applications. 16
Summary Worlds Best performing Silicon Germanium Photo-detector - Capable of operating at 40 Gbps - Low dark current and great responsivity - Details to be presented at Group IV conference Tokyo Japan Sept 20 th Background - Silicon is transparent to Infrared light and good for routing light - Germanium must be added to allow Silicon to absorb light - Intel used a unique process to grow Germanium on Silicon and produce an efficient Silicon Germanium photo-detector Vision - Build highly integrated Si Photonics chips for optical communication - Build using high-volume, low cost manufacturing processes - Enables terabit optical links 17
Links Silicon Photonics at Intel site - http://techresearch.intel.com/articles/tera- Scale/1419.htm Blog about recent modulator advance - http://blogs.intel.com/research/2007/07/40g_mod ulator.html 18
What We are Announcing Worlds Best performing Silicon Germanium Photodetector - Capable of operating at 40 Gbps - Low dark current and great responsivity - Details to be presented at Group IV conference Tokyo Japan Sept 20 th Background - Silicon is transparent to Infrared light and good for routing light - Germanium must be added to allow Silicon to absorb light - Intel used a unique process to grow Germanium on Silicon and produce an efficient Silicon Germanium photo-detector Vision - Build highly integrated Si Photonics chips for optical communication - Build using high-volume, low cost manufacturing processes - Enables terabit optical links for tera scale platforms 19
DC Photodetector Performance 10-2 Current (A) 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 Dark current Photocurrent -5-4 -3-2 -1 0 1 Voltage (V) Quantum efficiency (%) 100 80 60 40 20 50 μm long PD 100 μm long PD 1500 1530 1560 1590 1620 Wavelength (nm) Dark current of photodetector is still below noise floor of amplification circuitry. Quantum efficiency is excellent at ~95%. 21