以有機金屬化學氣相沉積法成長磷化銦於砷化鎵基板之研究

本論文使用有機金屬化學氣相沉積法(MOCVD)成長磷化銦薄膜於砷化鎵基板上，由於砷化鎵(GaAs)與磷化銦(InP)兩者之間存在著3.8 %的晶格不匹配，因此在磊晶時會產生許多的缺陷，導致磊晶品質尚有極大改善空間,也因此使得目前磷化銦的應用還是受到諸多限制，為了解決上述問題本研究以兩階段成長法(Two-step growth technique)先以低溫成長厚度20~50 nm磷化銦(LT-InP)薄膜作為成核層(Nucleation layer)，隨後升溫至700 °C成長厚度約0.4 μm之單晶HT-InP薄膜，來降低異質接面間的缺陷，並以不同溫度以及前驅物V/III比的調變來改善薄膜的品質並進行分析及探討。由實驗結果顯示，當 LT-InP的成長溫度逐由425 °C上升至475 °C時，X光繞射儀所量到的搖擺曲線的半高寬也逐漸上升，代表著InP單晶品質逐漸劣化，由此可知低溫成核層之成長溫度不宜過高，以防止HT-InP薄膜呈現多晶的狀況。另外LT-InP成核層的III族前驅物流量也不應過低，以防LT-InP成核層無法完整覆蓋於所要成長之表面上。最後以較佳LT-InP成核層之成長條件(溫度450 °C、TMIn流量900 slm、厚度20 nm)，然後在其上成長厚度2 μm的HT-InP薄膜，當HT-InP成長溫度為675 °C時，其XRD半高寬僅461 arcsec。雖然該薄膜之XRD半高寬值已可與其他研究相關之文獻結果相比擬，但InP薄膜品質仍有改善之空間。

關鍵字

有機金屬化學氣相沉積法；磷化銦薄膜；兩階段成長法

並列摘要

In this thesis, a low-pressure metal-organic chemical vapor deposition system (MOCVD) is used to grow indium phosphide thin films on GaAs substrates. Owing to a high lattice match of 3.8 % between GaAs and InP, many defects will be generated during the hetero-epitaxial process. There is still room for improvement in the epitaxial quality, which also makes the application of present indium phosphide films be subject to many restrictions. To solve the lattice misfit problems, this study uses a two-step growth technique. In which, firstly an indium phosphide nucleation layer (LT-InP) with a thickness of 20-50 nm was grown at a low temperature range of 425 – 475 °C. Then, the temperature is raised to 700 °C for the growth of good-quality top layer (HT-InP) with a thickness of about 0.4 μm. The growth parameters including the V/III ratio of the raw materials the growth temperature and the growth thickness have been modulated to determine optimal growth conditions for LT-InP layer. It is found that when the growth temperature of LT-InP is increased from 425°C to 475°C, the full width at half maximum of the X-ray rocking curve (XRD FWHM) for the HT-InP film also increases. This result demonstrated that good-quality HT-InP film can be obtained by optimizing the growth temperature of nucleation layer. It was also found that the growth temperature of nucleation layer should not be too high to prevent the HT-InP film from showing a polycrystalline state. In addition, the gas flow rate of Group III precursor for the nucleation layer growth should also be optimized to prevent an incomplete coverage of InP nucleation on the GaAs substrate. Finally, an HT-InP film with a thickness of 2 μm was grown on top under the optimized growth conditions of the LT-InP nucleation layer (growth temperature: 450 °C, TMIn flow rate: 900 slm, thickness: 20 nm). As for the HT-InP growth, when it was grown at 675 °C, its XRD FWHM is only 461 arcsec. Through the present study, it was found that the highly mismatched hetero-epitaxial structure of InP on GaAs can be prepared by a simple two-step growth technique with the top film quality analogous to other related literature.