砷化鎵/矽異質磊晶成長之結構與光學特性研究

本論文研究矽基板表面結構以及磊晶成長於矽基板上之砷化鎵結構與光學特性分析。主要分成兩個主題：第一部分透過穿隧電流掃描影像，探討經由不同製程方式做表面處理後，矽基板表面形貌之變化。實驗發現，標準(001)方向之矽基板，表面交錯分布A、B型階梯，高度落差為單層原子；然而，偏高角度基板表面主要為雙層原子高度的Ｂ型階梯(DB)，但於邊界有許多單層原子高度差的Kink。標準(001)方向之矽基板經由以氯氣為主要反應氣體的電漿蝕刻後，表面之B型單層原子層從56%縮小至14%，而趨向雙原子高之A型階梯，A型階梯不易產生Kink而較為穩定。相對於傳統透過偏角度或加熱技術來達成DB表面，以氯氣為主的電漿蝕刻提供了另一種達成雙層原子表面之方式，具有消除反相位晶界(antiphase boundary)的可能性。第二部分研究砷化鎵成長於矽基板之結構與光學特性。首先，存在反相位晶界的樣品，SEM照片呈現兩種不同晶向，透過計算此兩種晶向的面積比例，我們發現矽基板表面經氯氣為主的電漿蝕刻後，對於成長砷化鎵薄膜，有造成單一晶向的趨勢。由於砷化鎵與矽基板之熱膨脹係數不匹配，磊晶成長後降溫將造成拉伸應力，此應力在低溫12K約為2.19×10-3而在室溫下約為1.5×10-3，與理論計算相近。其次，研究反相位晶界在砷化鎵晶體中所造成的特性變化。在能隙間(Inner-band)的缺陷放光研究中顯示，反相位晶界的存在會抑制整體載子放光，且阻擋矽原子的內部擴散。且這種結構上的缺陷，在拉曼頻譜上造成被禁止的TO聲子強度增加，且降低砷化鎵在XRD(004)的強度。進一步利用拉曼與螢光電子在反相位晶界上聚焦量測，皆看到頻譜紅移現象，推測為反相位晶界造成、沿著平行於Ga-Ga或As-As鍵結的方向的一維拉伸應力。最後探討反相位晶界對砷化鎵XRD(002)繞射造成的影響，實驗證明了因反相位晶界的出現使得砷化鎵XRD(002)繞射強度降低，並觀察到反相位晶界造成XRD(002)譜形不對稱之現象。

關鍵字

異質磊晶；砷化鎵；矽基板表面；反相位晶界

並列摘要

In this thesis, we study the surface topography of silicon and its effects on the structural and optical properties of GaAs grown on Si. In the first part of this study, we used Scanning Tunneling Microscopy to investigate the Si surfaces with and without the treatment of Cl-based plasma. For surfaces without treatment, we observed that exact (001) Si surface contains only single-atomic-height steps with alternating SA and SB steps, while the vicinal Si (001) shows a dominance of biatomic-height steps (DB) accompanied with high density of single-atomic-height kinks. For the exact (001) surface with the treatment of Cl-based plasma, significant reduction of SB terrace was observed. The SB to SA terrace-area ratio is only 14% : 86%. The reduction of SB terrace makes the steps very similar to double-A steps (DA), which could open an alternative approach for anti-phase boundary (APB)-free III-V/Si growth. In the second part of this study, the structural and optical properties of GaAs epitaxial layer on Si were investigated. From low temperature photoluminescence (PL), X-ray diffractometry (XRD) and Raman scattering, we observed a residual tensile strain resulting from the thermal expansion coefficient mismatch between GaAs and Si. The strain determined from above measurement is 2.19x10-3 at 12K and 1.5x10-3 at 300K, which is consistent to our theoretical calculation. For GaAs grown on exact (001) Si, we observed two types of anti-phase domains (APDs) with ripples along [110] and [1-10] orientation, respectively, from SEM viewgraphs. These two type APDs are interlaced on the surface. For the sample with the Cl-based treatment, one of the APD types dominates over the other one in terms of surface area, suggesting the improvement on APB problems with the treatment. By comparing the PL inner-band of the samples, we found that APBs act as nonradiative recombination centers to suppress the PL intensity and prevent the inter-diffusion of Si atoms into GaAs. In additions, from the results of Raman scattering and XRD, APBs enhance the forbidden TO mode, degrades the intensity XRD (004) reflection, which could be attributed to the structural disordering induced by APBs. We also used micro-Raman and cathodoluminescence (CL) to probe the boundaries of APDs and found a frequency downshift in Raman scattering and a red shift in CL, implying the existence of a uni-axial strain along the boundaries. In additions, we also observed the expected decrease of XRD (002) reflection in samples with APDs.

並列關鍵字

Heteroepitaxy ； GaAs ； Si surface ； Antiphase boundary.

參考文獻

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國際替代計量

砷化鎵/矽異質磊晶成長之結構與光學特性研究

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