Malaysian Journal of Analytical Sciences Vol 19 No 6 (2015): 1229 - 1242

 

 

 

HETEROEPITAXIAL GROWTH OF VACUUM-EVAPORATED Si-Ge FILMS ON NANOSTRUCTURED SILICON SUBSTRATES

 

(Pertumbuhan Epitaksi Filem Si-Ge Menggunakan Kaedah Evaporasi Vakum Diatas

Silikon Berstruktur Nano)

 

Ayu Wazira Azhari^1,2*, Kamaruzzaman Sopian¹, Saleem Hussain Zaidi¹

 

¹Solar Energy Research Institute,

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

²School of Environmental Engineering,

Universiti Malaysia Perlis, 01000 Kangar, Perlis, Malaysia

 

*Corresponding author: ayuwazira@unimap.edu.my

 

 

Received: 8 February 2015 ; Accepted: 29 September 2015

 

 

Abstract

In this study, a low-cost vacuum-evaporated technique is used in the heteroepitaxial growth of Si-Ge films. Three different surface variations are employed: i.e. polished Si, Si micropyramids and Si nanopillars profiles. A simple metal-assisted chemical etching method is used to fabricate the Si nanopillars, with Ag acting as a catalyst. Following deposition, substrates are subjected to post-deposition thermal annealing at 1000^oC to improve the crystallinity of the Ge layer. Optical and morphological studies of surface area are conducted using field emission scanning electron microscopy (FE-SEM), Energy Dispersive X-ray (EDX), Raman spectroscopy and infrared spectroscopy. From the infrared spectroscopy analysis, the energy bandgap for Si-Ge films is estimated to be around 0.94 eV. This high-quality Si-Ge film is most favourable for optics, optoelectronics and high-efficiency solar cell applications.

 

Keywords: heteroepitaxial growth, silicon germanium, thermal evaporation, nanostructured Si, metal assisted chemical etching        

 

Abstrak

Dalam kajian ini, teknik evaporasi vakum berkos rendah digunakan dalam pertumbuhan epitaksi filem Si-Ge. Tiga variasi permukaan digunakan iaitu permukaan licin, permukaan berstruktur mikro-piramid dan permukaan berstruktur nano tiang. Satu kaedah berkos rendah berdasarkan kepada teknik punaran kimia terbantu logam (MACE) dengan perak (Ag) sebagai pemangkin telah dibangunkan untuk membentuk permukaan berstruktur nano. Selepas pemendapan, lapisan amorfus Ge kemudiannya menghablur di dalam relau penyepuhlindapan pada suhu 1000^oC menghasilkan pertumbuhan epitaksi lapisan Ge dan Si-Ge_. Lapisan Ge dan Si-Ge ini kemudiannya dicirikan menggunakan FESEM, EDX, spektroskopi Raman dan spektroskopi inframerah. Daripada pencirian analisi pektroskopi inframerah, julat jalur tenaga dianggarkan sekitar 0.94 eV. Filem Si-Ge berkualiti tinggi ini amat sesuai untuk aplikasi optik, opto-elektronik dan sel suria berkecekapan tinggi.      

 

Kata kunci:    pertumbuhan epitaksi, silicon germanium, evaporasi terma, Si berstruktur nano, punaran kimia terbantu logam

 

References

1.       Winkler, C. (1886). Germanium, Ge, ein neues, nichtmetallisches Element. Berichte der deutschen chemischen Gesellschaft, 19 (1): 210-211.

2.       Brattain, W. H. and Bardeen, J. (1948). Nature of the forward current in germanium point contacts [15]. Physical Review, 74 (2): 231-232.

3.       William F. Brinkman, Douglas E. Haggan and Troutman, W. W. (1997). A History of the Invention of the Transistor and Where It Will Lead Us. IEEE Journal of Solid-state Circuits, 32 (12): 1858 - 1865.

4.       Depuydt, B., Theuwis, A. and Romandic, I. (2006). Germanium: From the first application of Czochralski crystal growth to large diameter dislocation-free wafers. Materials Science in Semiconductor Processing, 9: 437–443.

5.       Schubert, M. B., Weller, H. C., Eberhardt, K. and Bauer, G. H. (1989). Structural Properties of a-Sil-xGex:H. Journal of Non-Crystalline Solids,  (114): 528 - 530.

6.       Yang, S.-H. and Lee, W.-J. (1985). Preparation of Hydrogenated Amorphous Germanium by Reactive Thermal Evaporation. Solid State Communications, 53 (11): 993-995.

7.       Said, K., Poortmans, J., Caymax, M., Loo, R., Daami, A., Bremond, G., Kruger, O. and Kittlerc, M. (1999). High quality, relaxed SiGe epitaxial layers for solar cell application. Thin Solid Films, (337): 85-89.

8.       Wang, C.-C., Liu, C.-Y., Lien, S.-Y., Weng, K.-W., Huang, J.-J., Chen, C.-F. and Wuu, D.-S. (2011). Hydrogenated amorphous silicon–germanium thin films with a narrow band gap for silicon-based solar cells. Current Applied Physics, 11 (1): S50-S53.

9.       Rosenberg, E. (2009). Germanium: environmental occurrence, importance and speciation. Review Environment Science and Biotechnology, 8 (29–57): 29-57.

10.    Vanamu, G., Datye, A. K., Dawson, R. and Zaidi, S. H. (2006). Growth of high-quality GaAs on Ge∕Si[sub 1−x]Ge[sub x] on nanostructured silicon substrates. Applied Physics Letters, 88 (25): 251909.

11.    Matthews, J. W. and Blakeslee, A. E. (1974). Defects in epitaxial multilayers: I. Misfit dislocations. Journal of Crystal Growth, 27: 118-125.

12.    Kasper, E. (2008). Current topics of silicon germanium devices. Applied Surface Science, 254 (19): 6158-6161.

13.    Fan, Q. H., Chen, C., Liao, X., Xiang, X., Zhang, S., Ingler, W., Adiga, N., Hu, Z., Cao, X. and Du, W. (2010). High efficiency silicon–germanium thin film solar cells using graded absorber layer. Solar Energy Materials and Solar Cells, 94 (7): 1300-1302.

14.    Datta, S., Xu, Y., Mahan, A. H., Branz, H. M. and Cohen, J. D. (2006). Superior structural and electronic properties for amorphous silicon–germanium alloys deposited by a low temperature hot wire chemical vapor deposition process. Journal of Non-Crystalline Solids, 352 (9-20): 1250-1254.

15.    Shah, V. A., Dobbie, A., Myronov, M. and Leadley, D. R. (2011). High quality relaxed Ge layers grown directly on a Si(001) substrate. Solid-State Electronics, 62 (1): 189-194.

16.    Chen, C., Zhou, Z., Chen, Y., Li, C., Lai, H. and Chen, S. (2010). Thermal stability of SiGe films on an ultra thin Ge buffer layer on Si grown at low temperature. Applied Surface Science, 256 (22): 6936-6940.

17.    Renrong, L., Jing, W. and Jun, X. (2009). Fabrication of High Quality SiGe Virtual Substrates by Combining Misfit Strain and Point Defect Techniques. Tsinghua Science and Technology, 14 (1): 62-67.

18.    Gentile, P., Eymery, J., Leroy, F., Fournel, F., Meziere, J. and Perreaub, P. (2005). Germanium growth on nanopatterned surface studied by STM. Journal of Crystal Growth 275: 1609–1613.

19.    Vanamu, G., Datye, A. K. and Zaidi, S. H. (2005). Growth of high quality Ge∕Si[sub 1−x]Ge[sub x] on nano-scale patterned Si structures. Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures. 23 (4): 1622.

20.    Vanamu, G., Datye, A. K. and Zaidi, S. H. (2005). Heteroepitaxial growth on microscale patterned silicon structures. Journal of Crystal Growth, 280 (1-2): 66-74.

21.    Vanamu, G., Datye, A. K. and Zaidi, S. H. (2006). Epitaxial growth of high-quality Ge films on nanostructured silicon substrates. Applied Physics Letters, 88 (20): 204104.

22.    Sorianello, V., Colace, L., Assanto, G., Notargiacomo, A., Armani, N., Rossi, F. and Ferrari, C. (2011). Thermal evaporation of Ge on Si for near infrared detectors: Material and device characterization. Microelectronic Engineering, 88: 526–529.

23.    Chen, Y.-H., Liu, J.-C., Chen, Y.-R., Lin, J.-W., Chen, C.-H., Lu, W.-H. and Li, C.-N. (2013). Enhancing performance of amorphous SiGe single junction solar cells by post-deposition thermal annealing. Thin Solid Films, 529: 7-9.

24.    Chartier, C., Bastide, S. and Lévy-Clément, C. (2008). Metal-assisted chemical etching of silicon in HF–H2O2. Electrochimica Acta, 53 (17): 5509-5516.

25.    Ashour, E. S. M., M.Y.Sulaiman, Amin, N. and Ibrahim, Z. (2012). Characterization of Si nanowires synthesized using metal-assisted wet-chemical etching. Malaysian Journal of Fundamental & Applied Sciences,  8 (3): 137 - 142.

26.    Smith, Z. R., Smith, R. L. and Collins, S. D. (2013). Mechanism of nanowire formation in metal assisted chemical etching. Electrochimica Acta, 92: 139-147.

27.    Tsujino, K. and Matsumura, M. (2007). Morphology of nanoholes formed in silicon by wet etching in solutions containing HF and H2O2 at different concentrations using silver nanoparticles as catalysts. Electrochimica Acta, 53 (1): 28-34.

28.    Bai, F., Li, M., Song, D., Yu, H., Jiang, B. and Li, Y. (2012). One-step synthesis of lighly doped porous silicon nanowires in HF/AgNO3/H2O2 solution at room temperature. Journal of Solid State Chemistry, 196: 596-600.

29.    Li, X. (2012). Metal assisted chemical etching for high aspect ratio nanostructures: A review of characteristics and applications in photovoltaics. Current Opinion in Solid State and Materials Science. 16 (2): 71-81.

30.    Zhong, X., Qu, Y., Lin, Y.-C., Liao, L. and Duan, X. (2011). Unveiling the Formation Pathway of Single Crystalline Porous Silicon Nanowires. ACS Applied Material Interfaces, 3 (2): 261-270.

31.    Kasper, E. (1996). Silicium germanium heterodevices. Applied Surface Science, 102 189-193.

32.    Kasper, E. and Heim, S. (2004). Challenges of high Ge content silicon germanium structures. Applied Surface Science, 224 (1-4): 3-8.

33.    Chen, P. S., Lee, S. W., Lee, M. H. and Liu, C. W. (2008). Formation of relaxed SiGe on the buffer consists of modified SiGe stacked layers by Si pre-intermixing. Applied Surface Science, 254 6076–6080.

34.    Rahim, A. F. A., Hashim, M. R., Ali, N. K., Rusop, M., Ooi, M. D. J. and Yusoff, M. Z. M. (2013). Self-assembled Ge islands and nanocrystals by RF magnetron sputtering and rapid thermal processing: The role of annealing temperature. Applied Surface Science, 275 193-200.

35.    Jadkar, S. R., Sali, J. V., Kshirsagar, S. T. and Takwale, M. G. (2002). Narrow band gap, high photosensitivity a-SiGe:H films prepared by hot wire chemical vapor deposition (HW-CVD) method. Materials Letters, 52: 399-403.

36.    Soukup, R. J., Ianno, N. J., Darveau, S. A. and Exstrom, C. L. (2005). Thin films of a-SiGe:H with device quality properties prepared by a novel hollow cathode deposition technique. Solar Energy Materials and Solar Cells 87 (1-4): 87-98.

37.    Coonan, B. P., Griffna, N., Beechinor, J. T., Murtagh, M., Redmond, G., Crean, G. M., HollaèNder, B., Mantl, S., Bozzo, S., Lazzari, J.-L., D'avitaya, F. A., Derrien, J. and Paul, D. J. (2000). Investigation of Si/SiGe heterostructure material using non-destructive optical techniques. Thin Solid Films, 364 75-79.