以分子束磊晶法磊晶成長鎘化物薄膜之探討

Investigating epitaxial growth of Cd-based thin films by molecular beam epitaxy

蔡育軒(Yu-Hsuan Tsai)

指導教授 ： 王智祥

中原大學/理學院/物理研究所/博士(2014年)

https://doi.org/10.6840/cycu201400949

摘要

本論文以分子束磊晶法分別在(100)砷化鎵、(100)向<111>偏6 度
矽基板以及(111)矽基板上成長鎘化合物，並藉由反射式高能電子繞射儀、掃描式電子顯微鏡、光激螢光光譜、X 光繞射等實驗探討磊晶層特性。首先，我們在硒化鎘成長於與其晶格不匹配的砷化鎵上，過程中發現加入少量的碲原子，能夠大幅提升硒化鎘磊晶層的品質。接著我們將硒化鎘磊晶層成長於矽基板上。將二元化合物成長於矽基板上常會有反相邊界問題，因此我們首先將硒化鎘成長於(100)向<111>偏6 度的矽基板，嘗試克服反相邊界問題，過程中觀察到硒化鎘磊晶層的品質都不好，而原因除了硒化鎘與矽有相當大的晶格不匹配外，還因為(100)向<111>偏6 度的矽基板表面會有許多刻意製造出的雙原子層台階，當硒化鎘成長於台階時，會因晶格不匹配的關係在台階處額外產生許多的缺陷。(111)矽基板因切割偏差所產生的台階都是雙原子層台階，所以不需刻意將基板向某個方向切割，這會使(111)矽基板表面台階密度遠小於在偏角度(100)矽基板的台階密度。因此接著我們將硒化鎘成長在(111)矽基板上，過程中我們發現成長在(111)矽基板的硒化鎘磊晶層相較於成長在(100)向<111>偏6 度矽基板的硒化鎘磊晶層，品質是有所提升的，但由霍爾效應得到樣品的自由電子濃度都在1019 cm-3，這將使後續p 型摻雜的硒化鎘難以達成。最後我們使用文獻中建議的碲化鎘成長於(111)矽基板上，過程中發現碲化鎘的品質因錳原子的加入，磊晶層整體品質有大幅的提升，錳含量為37%碲化錳鎘的低溫光激螢光光譜的近能隙發光積分面積是未含錳樣品的270倍，而晶體轉動曲線的半高寬也由未含錳的342″改善到含錳37%樣品的165″。最後在碲化鋅鎘磊晶層中我們觀察到其晶體轉動曲線半高寬相較於碲化鎘與碲化錳鎘來的寬，推測是由於鋅在碲化鎘中的偏析係數較錳在碲化鎘中來的大，使得鋅在碲化鎘磊晶層中的成分分布不均。

關鍵字

硒化鎘 ； 碲化(錳)鎘 ； 分子束磊晶 ； (111)矽基板

並列摘要

In this thesis, we investigated the molecular beam epitaxial growth of Cd-based compounds on different substrates, including (100) GaAs,
(100) tilt toward <111> 6。Si and (111) Si substrates. The physical properties of epilayers were analyzed by reflection high energy electron
diffraction, scanning electron microscope, photoluminescence, X-ray diffraction and Hall effect, respectively. First of all, we demonstrate the improvement of zinc-blende CdSe on (100) GaAs substrates with a large lattice mismatch by introducing a small amount of Te atoms. Secondly,
the (100) tilt toward <111> 6。Si substrate was employed to avoided the anti phase boundary in CdSe films. The surface step density increased
with the substrate off-cut angle. However, the large lattice mismatch between CdSe and Si brought about more defects along the step resulting
in poor optical properties. The surface step of (111) Si substrates are double atomic height which allow to form anti phase boundary free CdSe
epilayers. Compared to the CdSe grown on the (100) tilt toward <111> 6。 Si substrate, the quality of CdSe epilayers grew on the (111) Si were
improved. But the heavily n-type CdSe epilayer will probably make the growth of epilayers with p-type doping difficult. Finally, the involvement
of the Mn atoms was revealed to improve the growth of CdTe(111)A on Si(111) substrates. With the increasing of the Mn content from 0% to 37%, the FWHM of the X-ray rocking curve was reduced from 342″ to 165". Moreover, the near band edge emission line integral intensity was increased by a factor of about 270 at 10 K. Owing to the large segregation coefficient of Zn in CdTe, the FWHM of X-ray rocking curve of CdZnTe was broader than that of CdTe and CdMnTe.

並列關鍵字

Si(111) ； molecular beam epitaxy ； CdSe ； Cd(Mn)Te

參考文獻

Letters 73 1991.

Takamoto, 2013 9th International Conference on Concentrator

Photovoltaic Systems 22-25 .

Physics Letters 92 103503.

[7]A. Ishizaka and Y. Shiraki, 1986 Journal of The Electrochemical