1. T-shaped quantum-wire laser M. Yoshita, Y. Hayamizu, Y. Takahashi, H. Itoh, T. Ihara, and H. Akiyama Institute for Solid State Physics, Univ. of Tokyo and CREST, JST L. N. Pfeiffer and K. W. West Bell Laboratories, Lucent Technologies JSPS-NUS, Japan-Singapore symposium (2004.11.2-3) 1. Formation of high-quality GaAs T-shaped quantum wires Cleaved-edge overgrowth with MBE, AFM, PL, PLE 2. Single-T-wire laser PL scan, Lasing, Absorption/Gain 3. Single-T-wire FET PL, PLE

2. T-shaped Quantum Wire (T-wire)

3. Cleaved-edge overgrowth with MBE In situ Cleave (001) MBE Growth (110) MBE Growth [110] [001] GaAs substrate 600 o C490 o C by L. N. Pfeiffer et al., APL 56, 1679 (1990).

4. 490C Growth (By Yoshita et al. JJAP 2001) Atomically flat interfaces High Quality T-wire ???

5. 490C Growth (By Yoshita et al. JJAP 2001) Atomically flat interfaces High Quality 510-600C Anneal T-wire !?

6. 490C Growth (By Yoshita et al. JJAP 2001) Atomically flat interfaces High Quality 510-600C Anneal T-wire !!?

7. 490C Growth (By Yoshita et al. JJAP 2001) Atomically flat interfaces High Quality 510-600C Anneal T-wire !!!!!

8. (001) and (110) surfaces of GaAs (001) (110) [001] [110] [001]

9. (Akiyama et al. APL 2003) PL and PLE spectra 1D free exciton small Stokes shift 1D continuum states arm well stem well T-wire

10. E-field // to wire _ to wire // to arm well I E-field

11. Cavity length 500  m Probability of Photon Probability of Electron Single quantum wire laser  =5x10 -4

12. Scanning micro-PL spectra Continuous PL peak over 20  m PL width < 1.3 meV scan T=5K T-wire stem well

13. 500  m gold-coated cavity Threshold 5mW (Hayamizu et al, APL 2002) Lasing in a single quantum wire

14. Single wire laser with 500  m gold-coated cavity

15. Transmittance for single Takahashi et al. unpublished Coupling efficiency = 20%

16. Absorption for single Takahashi et al. unpublished

17. Absorption at 300 K Takahashi et al. unpublished

18. Experiment for gain

19. Evolution of continuum Takahashi et al. unpublished

20. 1D electron-gas density 1D electron-gas-density control in a FET-type single quantum wire 14nmx6nm ehe eh

21. E f =6meV E f = 2meV m e =0.067 m 0 m h =0.105 m 0 E b =2meV

22. Optically pumped lasers Current injection lasers Threshold current? High differential gain? Fast modulation? Switch & Modulator Large non-linearity? Quantum-Wire Devices

23. Summary Thanks ! 1.GaAs T-shaped quantum wires (T-wires) are formed by cleaved- edge overgrowth with MBE. 2.Growth-interrupt anneals dramatically improve T-wire quality. 3.AFM : No atomic steps over 100  m. 4.PL : Sharp PL width (~1meV) improved by a factor of 10. 5.PLE : Observation of 1D free exciton, & 1D continuum states 6.Single wire lasing : The world thinnest laser (14nm x 6nm), 5-60K, 5mW threshold optical pumping power at 5K. 7.Strong absorption by a single wire 84/cm (98.5% absorption / 500  m) at exciton peak at 5K 8.Room-temperature exciton absorption observed in 20-wire laser. 9.Single-wire FET is formed and optically studied. 10.In progress : physics, current injection, amplification, modulation.

24. ここまで。 16-17 分のトーク。

25. Experiment

26. How to derive

27. Absorption for 20

28. Absorption coefficients

30. 1.Exciton peak and continuum onset decay without shift. 2.Gap between exciton and continuum is gradually filled. 3.Exciton changes to Fermi edge Electron-Hole Plasma Exciton Hayamizu et al. unpublished

31. Absorption at higher temperatures by Cassidy Hayamizu et al. unpublished

33. B. W. Hakki and T. L. Paoli JAP. 46 1299 (1974) ： Reflectivity ： Absorption coeff. D. T. Cassidy JAP. 56 3096 (1984) Absorption/gain measurement based on Cassidy’s analysis of Fabry-Perot-laser emission below threshold Free Spectral Range

34. 490 o C Growth High Quality T-wire Interface control by growth-interruption annealing (by M. Yoshita et al. JJAP 2001) Atomically flat interfaces 600 o C Anneal arm well 6nm stem well 14nm

35. (By Yoshita et al. APL 2002)

36. X - Charged Exciton X Exciton Electron plasma and minority hole eh ehe eheeeeeeee