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Jerry Meyer:

Jerry Meyer:. IV-VI LEAD SALTS MATERIALS FOR MID-IR OPTO-ELECTRONIC APPLICATIONS. 14 th Semiconducting and Insulating Materials Conference (SIMC XIV 2007), Fayetteville, Arkansas, May 15-20, 2007. Zhisheng Shi , F . Zhao, D. Ray, D. Li, S. Mukherjee, S. Jain, J. Kar, S.Elizondo *

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Jerry Meyer:

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  1. Jerry Meyer: IV-VI LEAD SALTS MATERIALS FOR MID-IR OPTO-ELECTRONIC APPLICATIONS 14th Semiconducting and Insulating Materials Conference (SIMC XIV 2007), Fayetteville, Arkansas, May 15-20, 2007 Zhisheng Shi, F. Zhao, D. Ray, D. Li, S. Mukherjee, S. Jain, J. Kar, S.Elizondo* School of Electrical and Computer Engineering, University of Oklahoma *Nanolight Inc Optoelectronic Group

  2. Z (1 1 1) Y X (-1 -1 1) (1 -1 -1) (1 -1 1) IV-VI LEAD SALT SEMICONDUCTORS • PbSe, PbTe, PbSnSe, PbSnSe • Direct bandgap semiconductor materials • Emission (cut-off) wavelength 3.5 – 30 um • PbSrSe –larger bandgap material

  3. BaF2 Cubic (CaF2) 6.20 19.8 10.4 Some Related Material Parameters Materials Crystal structure Melting Point ( oC) Lattice constant (Å)  (10-6 K-1) Bandgap Energy (eV) * Data determined in our Lab SrSe Cubic (NaCl) 1600 6.22* NA 3.94* (indirect) 4.18* (direct) PbSe Cubic (NaCl) 6.124* 19.4 0.265* SrS Cubic 2226 6.02 NA 4.7 Si Diamond 5.43095 2.6 1.124 CaF2 Cubic (CaF2) 5.464 19.2 12.1 IV-VI lead salt can be grown on Si and BaF2 substrate

  4. OPTO-ELECTRONIC APPLICATIONS (After Hans Zogg etc) • Mid-IR lasers for tunable absorption spectroscopic applications • Mid-IR Focal Plane Array

  5. MID-IR LASER APPLICATIONS • Trace-gas-sensing systems based on laser absorption spectroscopy • Scientific Research • Automobile Industry • Power Plants • Medicine • Environmental Control • Chemical, Pharmaceutical and Semiconductor Industries • Military base cleaning and chemical weapon detection • Potential Applications: • Countermeasure • Open path A-B Distance Wireless Communication Single mode, tunable, Narrow linewidth, cw mode, >0.3 mW High brightness, (quasi-)cw High speed Un-cooled or TE-cooled lasers are required/preferred

  6. Mid-IR tunable diode laser absorption spectroscopy for Gas sensing HF 2.52 mm CH4 3.3 mm HCl 3.47 mm CO2 4.25 mm N2O 4.5 mm CO 4.6 mm O3 4.73 mm NO 5.3 mm NH3 6.1 mm • The rotation and vibration modes of many gas molecules are in the mid-IR range. • The mid-IR tunable diode laser absorption spectroscopy (MIR TDLAS) offers “finger print” identification of the gas and its concentration. • The sensitivity of MIR TDLS could reach part per 10 billion Hundreds more can be found at EPA’s data base http://www.epa.gov/ttnemc01/ftir/refnam.html

  7. III-V QC Sb-based Type-II IV-VI Pb-salts dλ /dT 0.12 cm-1/K 0.61 cm-1/K 2.76 cm-1/K Current tuning range 1 – 2 cm-1 N/A ~ 20 cm-1 PbSe-BASED TUNABLE MID-IR LASERS Best emission range for PbSe-based materials: 3.5 – 10 mm Conventional IV-VI (100) orientated edge emitting lasers tend to have multi-mode emission and mode hopping with the single mode output power of about 0.5 mW

  8. Z (1 1 1) Y X (-1 -1 1) (1 -1 -1) (1 -1 1) OUR INNOVATION: NONE-[100] LASERS • For low dimensional structure such as QW • (100) growth stay degenerated • (111) Lift off the degeneracy • (110) Partially lift off the degeneracy

  9. NONE-[100] :LOW DISLOCATION DENSITY The Burgers vectors are of type a/2 <110> and the primary glide planes are {100} For (100) oriented layers, no glide can occur in the main {100} glide system For (111) growth orientation the strain can relax by the glide of dislocations on the {100} type planes since the Schmid factors are high H. Zogg, et al, Phys. Rev. B50, (10801)1994

  10. A NEW MID-IR LEAD SALT VCSEL ON (111) BaF2 SUBSTRATE 291 nm Pb0.85Sr0.15Se (R = 98%) /2 Active Region (8 QWs) (R = 99%) 235 nm Pb0.97Sr0.03Se (n = 1.5) (n = 4.7) Lead salt cleaves on {100} planes BaF2 cleaves on {111} planes F-P cavity is formed by two DBRs

  11. FIRST MID-IR LEAD SALT VCSELs(In collaboration with NRL – Dr. J. Meyer’s group) • MQW VCSEL • Tmax = 280 K • Pmax = 300 mW • Ith >10.5 kW/cm2 • (lowest Ith of all optically pumped laser) Bulk PbSe active region ( cavity) • Tmax = 289 K • Pmax = 38 mW • Ith 69 kW/cm2 • 100 ns pump Shi et al., Fall MRS (1999); APL 76, 3688 (2000); Bewley et al., Electron. Lett. 36, 539 (2000) C. L. Felix, et al., Appl. Phys. Lett. 78, 3770(2001)

  12. ABOVE ROOM TEMPERATURE PULSED OPERATION F. Zhao, H. Wu, L. Jayasinghe and Z. Shi, Appl. Phys. Lett., . 80, 1129(2002)

  13. OPTICALLY PUMPED CW OPERATION A QW VCSEL CW EMISSION AT 230K WITH EPI-SIDE UP MOUNTING F. Zhao, H. Wu, A. Majumdar and Z. Shi , Appl. Phys. Lett., 83, 5133 (2003)

  14. LIMITATIONS OF VCSEL Successful VCSEL development on [111] orientation: “newsbreaks” on “Laser Focus World” (July 2001 and May 2002), Reviewe“Compound semiconductors” (October 2001) “Photonic Spectra ” (July 2002) (http://www.photonics.com/Spectra/tech/may02/techOperates.asp) “Technology Horizons” (Sept 2002, p39) (http://www.afrlhorizons.com/Briefs/Sept02/OSR0204.html ) • Limitations: • Low output power because of small active region volume • Low tunability ~dl/dT = 0.88 cm-1/K Edge emitting lasers are preferred for gas sensing

  15. IV-VI GAIN ALONG DIFFERENT ORIENTATIONS Bulk material gain is almost the same for [100], [111] and [110] orientations For QW structure:[111] orientation has the lowest threshold [110] provides the highest gain Z. Shi, X. Lv, F. Zhao, A. Majumdar, D. Ray, R. Singh, X. J. Yan, “[110] Orientated Lead Salt Mid-Infrared Lasers”, Appl. Phys. Lett., to be published

  16. [110] Pb-salt Edge Emitting Laser Si3 N4 layer Top contact Insulating layer Active region bottom contact Room temperature cw operation is achieved with SEI structure because of better heat dissipation Xiaoliang Lu and Zhisheng Shi, “Theoretical Investigations of [110] IV-VI Lead Salt Edge-emitting Lasers”, submitted to IEEE J. Quan. Electron.

  17. FIRST MBE GROWTH OF LEAD SALT MATERIALS ON [110] ORIENTATION (110) BaF2 (110) PbSe [1¯12] azimuth [1¯12] azimuth (110) PbSe (110) PbSe [1¯1 0] azimuth [001] azimuth

  18. [220] HIGH RESOLUTION X-RAY DIFFRACTION Typical (222) rocking curves for PbSe thin films grown on (111) BaF2 substrates are between 90 and 150 arcsec. The dislocation density estimated from the rocking curve was 1x107 cm-2.

  19. Comparison of MQW PL between [111] and [110] orientated substrates PL intensity of [110] MQW structure was twice as high as the [111] structure from the same MBE run

  20. Preliminary Results of Electrically pumped [110]Pb-salt laser on PbSe [110] substrate Laser emission spectrum above threshold at 800mA injection current at 77K Laser emission spectra above threshold at different injection current at 77K Threshold current density was approximately 2.5 kA/cm2 From 500 to 600 mA, the peak emission wavelength can be tuned 14 cm-1; Current Tunability: 0.14 – 0.15 cm-1/ mA

  21. IV-VI Lead salt Microstructures Our research results:

  22. Optical Characterization for Microtubes Input Power Density: 3.8 kW/cm2 A. Majumdar et al. Applied Phys. Lett. 88, 1711111 (2006)

  23. Surface Side Emission inside a tube Proposed Applications 1126µm Intensity Wavenumbers (cm-1)

  24. Proposed Applications

  25. IMPROVEMENT ON THE EXISTING LEAD SALT DETECTOR ARRAYS ON Si — EVISIONED Hans Zogg, Alexander Fach, Joachim John, Jürg Masek, Peter Müller, Carmine Paglino, Stefan Blunier, “Photovoltaic IV-VI on Si infrared-sensor arrays for thermal imaging”, Opt. Engineering 34, (1964)1995

  26. A new p-n junction IV-VI Mid-IR detector on Si Challenges: Non-uniformities Quantum Efficiency, Cost • Advantages of Pb-salt Materials: • Coulomb scattering by ionized impurities is strongly suppressed because of the large dielectric constant • Growth temperature of Pb-salt materials is below 400 C º Direct growth of Pb-salt detector structures on Si with integrated ROICs. • Uniformity -reduces the demand for powerful signal processing of the ROICs Cost-effective monolithic FPA on a Si

  27. P-N Junction Over Schottky Pb-Salt Detector ~ MCT: D*~ 2.3x1011 cm Hz1/2/W PbSnSe (Schottky): D* ~ 2x1010 cm Hz1/2/W Comparable or better performance on p-n PbSnSe Detector anticipated

  28. Unetched (n-type) Etched (p-type) 1.3 μm 4.85 μm P-N Junction Over Schottky Pb-Salt Detector A New in situ MBE growth technique has been recently developed for PbSnSe on Si – a breakthrough for p-n junction detector fabrication

  29. A new p-n junction IV-VI Mid-IR detector on Si

  30. SUMMARY & FUTURE WORK • Successful lead salt mid-IR VCSEL development • [110] orientated IV-VI edge emitting lasers • IV-VI micro-structures • Mid-IR detector array on Si (110) substrate Future work • High temperature, single-mode mid-IR laser • Cost-effective monolithic FPA on Si substrate

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