砷化鎵三五族材料成長於矽奈米結構之異質磊晶與光學分析

Heteroepitaxy and Optical Characterization of GaAs III-V Materials Grown on Si Nanostructure

黃政穎(Cheng-Ying Huang)

指導教授 ： 林浩雄

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.10224

摘要

本論文研究砷化鎵材料異質磊晶於矽基板及矽奈米結構的成長與光學特性。第一部分研究砷化鎵成長於矽基板上會在介面處出現高密度的結構缺陷，例如: 介面差排、穿透差排、疊差、微雙晶、以及反相位晶界。然而，實驗發現當成長磊晶膜厚增加，結構缺陷密度可被大幅降低。另外，由於砷化鎵與矽基板熱膨脹係數的差異，在砷化鎵磊晶層中亦觀察到降溫過程產生的殘留拉伸應力。
第二部分研究發現低溫成長無法將砷化鎵磊晶於矽奈米溝渠，此乃因低溫成長會在溝渠側壁及淺溝渠絕緣氧化層上孕核，而後成長為多晶砷化鎵而封閉溝渠開口。利用定指向磊晶法與一階段高溫成長，砷化鎵可成功的選擇性磊晶於40奈米矽溝渠，據我們所知，此為目前文獻記載第一個使用氣態分子束磊晶法將砷化鎵填入40奈米溝渠的成果。利用穿透式電子顯微鏡進一步研究80奈米矽溝渠內的變質砷化鎵，發現砷化鎵內並無穿透差排與反相位晶界的出現，而僅有微雙晶與60度介面差排的產生，並且能有效的釋放晶格不匹配應變。穿透差排的消失可歸因於晶格不匹配應力和溝渠側壁的鏡像引力使得穿透差排滑移至溝渠側壁，而反相位晶界的消失則可能原於溝渠內僅有單一成核的成長。
最後，我們藉由拉曼光譜和陰極螢光光譜研究溝渠內砷化鎵的光學特性。拉曼結果發現砷化鎵產生強烈的TO聲子模態信號，並且不論砷化鎵是成長入[110]或[100]指向的溝渠，皆不遵守拉曼選擇規則，此可歸因於微雙晶的出現和多面向的表面。表面聲子(SO)模態亦被拉曼光譜觀測到。隨著溝渠寬度減小，SO聲子峰值逐漸的向TO聲子接近，而其強度也逐漸增強。陰極螢光光譜顯示溝渠內的砷化鎵出現強烈的帶間躍遷放光，顯示溝渠內砷化鎵的非輻射中心大幅度的減少，並且有相當好的磊晶品質。

關鍵字

砷化鎵 ； 矽奈米結構 ； 分子束磊晶法

並列摘要

In this thesis, the heteroepitaxy and optical properties of GaAs grown on planar Si wafer and Si nanostructure by gas-source molecular beam epitaxy (GSMBE) have been investigated. First, the GaAs on planar Si wafer contains high density of structural defects such as misfit dislocations, threading dislocations, stacking faults, microtwins, and antiphase boundaries, which are mostly around the GaAs/Si interface. However, the density of structural defects is significantly reduced with the increment of epilayer thickness. Additionally, the residual tensile strain in GaAs epilayer, resulting from the mismatch of thermal expansion coefficient between GaAs and Si, is also observed.
On the growth of GaAs in Si nano-trenches, the low temperature deposition is incapable of filling GaAs into Si nano-trenches due to the nucleation of GaAs on the trench sidewall and shallow-trench-isolation oxide, which could further develop to thick polycrystalline GaAs layer and seal the trench opening. With orient-beam epitaxy and high temperature one-step growth, high-quality GaAs is selectively grown in 40-nm-wide Si trenches successfully. To our knowledge, it is the first accomplishment of GaAs grown in 40-nm Si trenches by GSMBE. Furthermore, a metamorphic GaAs in 80-nm Si trench was investigated in detail by cross-sectional transmission electron microscopy. The results indicate that no threading dislocations and antiphase boundaries exist in epitaxial GaAs; only microtwins and 60° misfit dislocations are generated, which can efficiently relieve the lattice misfit strain. The disappearance of threading dislocations could be attributed to the large lattice misfit stress and the sidewall image force, which could drive the threading dislocations to glide to the sidewall. The disappearance of antiphase boundaries is probably due to single nucleus growth in the trench.
Finally, the optical properties of GaAs in Si nano-trenches were studied by Raman spectroscopy and cathodoluminescence spectroscopy at room temperature. Irrespective to trench orientation along [110] or [100], strong TO phonon mode is observed in Raman spectra, indicating that the breakdown of Raman selection rule due to the presence of microtwins and surface faceting. Surface optical (SO) phonon mode is also observed in this study. With the decrement of trench width, SO phonon peak slightly shifts to TO phonon and its intensity increases as well. The cathodoluminescence result reveals a strong band-to-band emission of GaAs in Si nano-trenches, indicative of a significant reduction of non-radiative centers and the good crystalline quality.

並列關鍵字

GaAs ； Si Nanostructure ； MBE

參考文獻

[52] J. Johansson, L. S. Karlsson, C. P. T. Svensson, T. Mårtensson, B. A. Wacaser, K. eppert, L. Samuelson, and W. Seifert, “Structural properties of <111>B-oriented III–V nanowires,” Nature Mater., vol. 5, pp. 574-580, 2006.

[1] P. K. Bondyopadhyay, “Moore’s law governs the silicon revolution,” Proc. IEEE, vol. 86, pp. 78-81, 1998.

[2] D. J. Frank, R. H. Dennard, E. Nowak, P. M. Solomon, Y. Taur, and H. S. P. Wong, “Device scaling limits of Si MOSFETs and their application dependencies,” Proc. IEEE, vol. 89, pp. 259-288, 2001.

[3] M. L. Lee, E. A. Fitzgerald, M. T. Bulsara, M. T. Currie, and A. Lochtefeld, “Strained Si, SiGe, and Ge channels for high-mobility metal-oxide-semiconductor field-effect transistors,” J. Appl. Phys., vol. 97, p. 011101, 2005.

[6] Semiconductor Industry Association (SIA), International Technology Roadmap for Semiconductors, 2007 edition, San Jose, CA.