本論文主要研究以氣態源分子束磊晶法成長之量子點與量子井複合結構之光學性質。吾人藉由光子調制反射光譜、光激發螢光光譜與表面光電壓光譜量測技術來探討其光學性質。光子調制反射光譜可以讓吾人分析砷化鎵之FKO以了解其內建電場強度。藉由表面光電壓光譜量測，吾人可於室溫下清楚觀察到量子點、量子井、濕層以及砷化鎵的躍遷訊號。低溫下之激發源功率相依之光激發螢光光譜實驗結果中，吾人不僅可以觀察到砷化銦量子點的基態與激發態訊號，亦可以發現量子點的訊號峰值位置不會隨著激發源功率的改變而有顯著的變化：另外，對於銻砷化鎵/砷化鎵量子井峰值位置則會隨著激發功率的增加，其有明顯的藍移。依據銻砷化鎵/砷化鎵量子井的激發源功率相依之光激發螢光光譜結果，吾人可以判斷此為第二型量子井能帶結構。根據量子點與量子井於激發源功率相依之光激發螢光光譜中的特徵表現，使吾人可以分辨量子點與量子井複合結構中的訊號源為量子點或量子井。對於間隔層厚度為10 nm之量子點與量子井複合結構，其量子點與量子井間並無顯著的耦合效應；對於間隔層厚度為5 nm之量子點與量子井複合結構，由於量子點與量子井間的耦合效應，可增加發光波長，此將有助於光纖通訊的發展應用。
藉由光子調制反射光譜、光激發螢光光譜與表面光電壓光譜量測技術，將有助於吾人瞭解量子點與量子井複合結構的光學性質。

Due to the type II band alignment, the electron and hole in a GaAsSb/GaAs strained quantum well (QW) are spatially separated. This configuration leads to the fundamental transition energy of QW being lower than the band gaps of the barrier and well. It is a great advantage in application of long wavelength lasers. However, the spatial separation of the electron and hole wavefunctions results in a low optical matrix element which leads to high threshold current density in GaAsSb/GaAs QW 1asers. One way to increase the matrix element is to enhance the confinement of the active medium. A composite structure consisting of a GaAsSb/GaAs QW and an adjacent InAs/GaAs self-assembled quantum dot (QD) has been proposed to improve the performance of the type-II laser diodes. In this composite structure, GaAs0.7Sb0.3 QW and a GaAs spacer layer were grown beneath InAs QDs. Since the strain exerted by InAs QDs on their bottom is tensile below the dots and compressive under the edge of the dots, the band diagram of the GaAs spacer and GaAsSb QW are modulated to form potential wells in the growth plane. As a result, both electrons and holes are trapped in the potential wells
induced InAs QDs. Along the growth direction, the type-II GaAs0.7Sb0.3/GaAs heterostructure provides the confinement of the third dimension.
In this thesis, a detailed optical characterization of this composite structure was carried out by using photoreflectance (PR), surface photovoltage spectroscopy (SPS) and photoluminescence (PL) techniques. The built-in electric field in the GaAs cap layer was determined by analyzing the GaAs-related Franz-Keldysh oscillations. The room temperature SPS spectra exhibit the features originated from QDs, QW, wetting layer, and GaAs cap-layer/barrier. The low-temperature PL band of the modulated potential wells in GaAs0.7Sb0.3 QW, resulting from the tensile strain exerted by the InAs QD stressor, shows a giant redshift as compared with the GaAs0.7Sb0.3 QW control sample at low excitation level. At higher temperature, the thermalization of carriers in QDs enhances the fluctuation of the potential wells, which provides extra quantum confinement for the carriers and enhances the luminescence intensity. This effect can be used to improve the performance of type-II GaAsSb/GaAs QW lasers. We demonstrated that PR, SPS and PL can be used as nondestructive powerful optical characterization techniques for
GaAs0.7Sb0.3/GaAs type-II quantum well with an adjacent InAs quantum-dot layer composite structure.

1. Maximov, M. V., Tsatsul’nikov, A. F., Volovik, B.V., Sizov, D. S., Shernyakov, Y. M., Kaiander, I. N., Zhukov, A. E., Kovsh, A. R., Mikhrin, S. S., Ustinov, V. M., Alferov, Z. I., heitz, R., Shchukin, V. A., Ledentsov, N. N., Bimberg, D., Musikhin, Y. G., and Neumann, W., “Tuning Quantum Dot Properties by Activated Phase Separation of an InGa(Al)As Alloy Grown on InAs Stressors,” Phys. Rev. B, Vol. 62,No. 24, pp. 16671-16680 (2000).

2. Arakawa, Y., and Sakaki, H., “Multidimensional quantum well laser and temperature dependent of its threshold current,” Appl. Phys. Lett., Vol. 40, No. 11, pp. 939-941 (1982).

3. Marzin, J. Y., Gerard, J. M., Izrael, A., Barrier, D., and Bastard, G., “Photoluminescence of Single InAs Quantum Dots Obtained by Self-Qrganized Growth on GaAs,” Phys. Rev. Lett., Vol. 73, No. 5, pp. 716-719 (1994).

4. Qianghua, X., Konkar, A., Kalburge, A., Ramachandran, T.R., Chen, P., Cartland, R., Madhukar, A., Lin, H. T., and Rich, D. H., “Structural and Optical Behavior of Strained InAs Quantim Boxes Grown on Planar and Patterned GaAs (100) Substrates by Molecular-Beam Epitaxy,” J. Vac. Sci. Techol. B, Vol. 13, No. 2, pp. 642-645 (1995).

5. Leonard, D., Krishnamurthy, M., Reaves, C. M., Denbaar, S. P., and Petroff, P. M., “Direct Formation of Quantum-Sized Dots from Uniform Coherent Islands of InGaAs on GaAs Surfaces,” Appl. Phys. Lett., Vol. 63, No. 23, pp. 3203-3205 (1993).

6. Heinrichsdorff, F., Krost, A., Grundmann, M., Bimberg, D., Kosogov, A., and Werner, P., “Self-Organization Processes of InGaAs/GaAs Quantum Dots Grown by Metalorganic Chemical Vapor Deposition,” Appl. Phys. Lett., Vol. 68, No. 23, pp. 3284-3286 (1996).

7. Bennett, B. R., Magno, R., and Shanabrook, B. V., “Molecular Beam Epitaxial Growth of InSb, GaSb, and AlSb Nanometer-Scale Dots on GaAs,” Appl. Phys. Lett., Vol. 68, No. 4, pp. 505-507 (1996).

8. Seifert, W., Carlsson, A., Petersson, A., Wernersson, L. E., and Samuelson, L., “Alignment of InP Stranski-Krastanow Dots by Growth on Patterned GaAs/GaInP Surfaces,” Appl. Phys. Lett., Vol. 68, No. 12, pp. 1684-1686 (1996).

9. Fafard, S., Wasilewski, Z., Mccaffrey, J., Raymond, S., and Charbonneau, S., “InAs Self-Assembled Quantum Dots on InP by Molecular Beam Epitaxy,” Appl. Phys. Lett., Vol. 68, No. 7, pp. 991-993 (1996).

10. Groenen, J., Mlayah, A., Carles, R., Ponchet, A., Corre, A. L., and Salaun, S., “Strain in InAs Islands Grown on InP(001) Analyzed by Raman Spectroscopy,” Appl. Phys. Lett., Vol. 69, N0. 7, pp. 943-945 (1996).

11. Sitarek, P., Hsu, H. P., Huang, Y. S., Lin, T. M., Lin, H. H., and Tiong, K. K., “Optical Studies of Type-I GaAs1-xSbx/GaAs Multiple Quantum Well Structures,” J. Appl. Phys., Vol. 105, pp. 123523-1∼123523-4 (2009).

12. Chiu, Y. S., Ya, M. H., Su, W. S., and Chen, Y. F., “Properties of Photoluminescence in Type-II GaAsSb/GaAs Multiple Quantum Wells,” J. Appl. Phys., Vol. 92, No. 10, pp. 5810-5813 (2002).

13. Chen, T. T., Chen, C. H., Cheng, W. Z., Su, W. S., Ya, M. H., Chen, Y. F., Liu, P. W., and Lin, H. H., “Optical Studies of Strained Type-II GaAs0.7Sb0.3/GaAs Multiple Quantum Wells,” J. Appl. Phys., Vol. 93, No. 12, pp. 9655-9658 (2003).

14. Teissier, R., Sicault, D., Harmand, J. C., Ungaro, G., Roux, G. Le., and Largeau, L., “Temperature-Dependent Valence Band Offset and Band-Gap Energies of Pseudomorphic GaAsSb on GaAs,” J. Appl. Phys., Vol. 89, No. 10, pp. 5473-5477 (2001).
15. Dinu, M., Cunningham, J. E., Quochi, F., and Shah, J., “Optical Properties of Strained Antimonide-Based Heterostructures,” J. Appl. Phys., Vol. 94, No. 3, pp. 1506-1512 (2003).

16. Liao, Y. A., Hsu, W. T., Lee, M. C., Chiu, P. C., Chyi , J. I., and Chang, W. H. “Time-Resolved Photoluminescence of Type-II InAs/GaAs Quantum Dots Covered by a Thin GaAs1-xSbx Layer,” Phys. Status Solidi C., Vol. 6, No. 6, pp. 1449-1452 (2009).

17. Liu, H. Y., Steer, M. J. Badcock, T. J., Mowbray, D. J., Skolnick, M. S., Suarez, F., Ng, J. S., Hopkinson, M., and David, J. P. R., “Room-Temperature 1.6μm Light Emission From InAs/GaAs Quantum Dots With a Thin GaAsSb Cap Layer,” J. Appl. Phys., Vol. 99, pp. 046104-1∼046104-3 (2006).

18. Lin, Y. R., Lai, Y. F. Liu, C. P., and Lin, H. H., “GaAs0.7Sb0.3/GaAs Type-II Quantum Well With an Adjacent InAs Quantum-Dot Stressor Layer,” Appl. Phys. Lett., Vol. 94, pp. 111106-1∼111106-3 (2009).

19. Seraphin, B. O., Hess, R. B., and Bottka, N.,“The Effect of an Electric Field on Reflectivity of Germanium,” J. Appl. Phys., Vol. 36, No. 7, pp. 2242-2250 (1965).

20. Kronik, L., Shapira, Y., “Surface Photovoltage Phenomena : theory, Experiment, and Applications,” Surf. Sci. Reports, Vol. 37, pp. 1-206 (1999).

21. Shapira, Y., Brillson, L., and Heller, A., “Origin of Surface and Metal-Induced Interface States in InP,” Phys. Rev. B, Vol. 29, No. 12, pp. 6824 - 6832 (1984).

22. Lüth, H., Büchel, M., Dorn, R., Liehr, M., and Matz, R., “Electronic Structure of Cleaved Clean and Oxygen-Covered GaAs (110) Surfaces,” Phys. Rew. B, Vol. 15, No. 2, pp. 865-874 (1997)

23. Ashkenasy, N. B., Kronik, L., Shapira, Y., Rosenwaks, Y., Hanna, M. C., Leibovitch, M., and Ram, P., “Surface Photovoltage Spectroscopy of Quantum Wells and Superlattices,” Appl. Phys. Lett., Vol. 68, No. 7, pp. 879-881 (1996).

24. Aigoui, L., Pollak, F. H., Petruzello, T. J., and Shahzad, K., “ Observation of Excitonic features in ZnSe/ZnMgSSe Multiple Quantum Wells by Normalized Kelvin Probe Spectroscopy at Low Temperatures,” Solid State Comm., Vol. 102, No. 12, pp. 877-882 (1997).

25. Mishori, B., Leibovitch, M., Shapira, Y., Pollak, F. H., Streit, D. C., and Woitowicz, M., “Surface Photovoltage Spectroscopy of a GaAs/AlGaAs Heterojunction Bipolar Transistor,” Appl. Phys. Lett., Vol. 73, No. 5, pp. 650-652 (1998).

26. Huang, Y. S., Malikova, L., Pollak, F. H., Shen, H., Pamulapati, J., and Newman, P., “Surface Photovoltage Spectroscopy, Photoreflectance, and Reflectivity Characterization of an InGaAs/GaAs/GaAlAs Vertical-Cavity Surface-Emitting Laser Including Temperature Dependent.” Appl. Phys. Lett., Vol. 77, No. 1, pp. 37–39 (2000).

27 Ashkenasy, N., Leibovitch, M., Shapira, Y., Pollak, F. H., Bumham, G. T., and Wang, X., “ Surface Photovoltage Spectroscopy of InGaAs/GaAs/AlGaAs Single Quantum Well Laser Structure,” J. Appl. Phys., Vol. 83, pp. 1146–1149 (1998).

28. Chan, C. H., Chen, H. S., Kao, C. W., Hsu, H. P., Huang, Y. S., and Wang, J. S., “ Investigation of Multilayer Electronic Vertically Coupled InAs/GaAs Quantum Dot Structures Using Surface Photovoltage Spectroscopy,” Appl. Phys. Lett., Vol. 89, pp. 022114-1∼022114-3 (2006).
29. Kallergi, N., Roughani, B., Aubel, J., and Sundaram, S., “Correlation of Interference Effects in Photoreflectance Spectra with GaAs Homolayer Thickness,” J. Appl. Phys., Vol. 68, No. 9, pp. 4656-4661 (1990).

30. Huang, D., Mui, D., and Morkoc, H., “Interference Effects Probed by Photoreflectance Spectrascopy,” J. Appl. Phys., Vol. 66, No. 1, pp. 358-361 (1989).

31. Kudrawiec, R., Sitarek, P., Misiewicz, J., Bank, S. R., Yuen, H. B., Wistey, M. A., and Harris, Jr. James S., “Interference Effects in Electromodulation Spectroscopy Applied to GaAs-based Structures : A Comparison of Photoreflectance and Contactless Electroreflectance,” Appl. Phys. Lett., Vol. 86, pp. 091115-1∼091115-3 (2005).

32. Lipsanen, H. K., and Airasinen, “Interference Effects in Photoreflectance of Epitaxial Layers Grown on Semi-insulating substrates,” Appl. Phys. Lett., Vol. 63, No. 21, pp. 2863-2865 (1993).

33. Aigouy, L., Holden, T., Pollak, F. H., Ledentsov, N. N., Ustinov, W. M., Kop’ev, P. S., and Bimberg, D., “Contactless Electroreflectance Study of a Vertically Coupled Quantum Dot-Based InAs/GaAs Layer Structure,” Appl. Phys. Lett., Vol. 70, No. 25, pp. 3329-3331 (1997).

34. Lin., C. M., and Chen, Y. F., “Properties of Photoluminescence in Type-II ZnMnSe/ZnSeTe Multiple Quantum Wells,” Appl. Phys. Lett., Vol. 85, No. 13, pp. 2544-2546 (2004).

35. Dinu, M., Cunningham, J. E., Quochi, F., and Shah, J., “ Optical Properties of Strained Antimonide-Based Heterostructures,” J. Appl. Phys., Vol. 94, No. 3, pp. 1506-1512 (2003).