以迴旋濺鍍法製作AlN/GaN異質結構之二維電子氣特性研究

The Characteristic study of 2-D electron gas induced in AlN/GaN heterojunction using Helicon Sputtering system

吳俊德(Chun-Te Wu)

指導教授 ： 高慧玲

中原大學/工學院/電子工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400312

摘要

AlGaN/GaN 異質結構場效電晶體近年來在高頻、高功率微波領域上一直是個熱門的研究課題，常運用於下列元件：低雜訊微波放大器、功率微波放大器、高溫元件以及電源供應(power supplier)。但是其卻也有不少的缺點，如隨著鋁的含量越高，其介面間的不匹配程度將會提高，導致介面間的缺陷增加，片載子濃度和遷移率都將受缺陷影響降低。
因此，有一些其他的研究團隊提出使用AlN/GaN這種異質結構，此種結構只要能克服AlN成長在GaN上容易造成缺陷的問題，由於氮化鋁的極化效應比氮化鋁鎵更強，所以AlN/GaN異質結構將有更高的片載子濃度，且氮化鋁為二元的材料能有效降低合金散射的現象，使其遷移率不至於嚴重的衰減，能得到較AlGaN/GaN 異質結構更佳的特性。
本研究之目的是在GaN/Sapphire基板上低溫成長AlN的磊晶薄膜，並探討各種濺鍍條件對AlN薄膜品質的影響，以及研究AlN/GaN介面所感應之二維電子氣現象，證實介面間受極化效應感應產生的二維電子氣確實存在。
我們成功的在低溫下(300℃)，利用迴旋濺鍍系統在GaN/Sapphire基板上成長出高品質的AlN磊晶薄膜，其(002)排向氮化鋁薄膜Rocking　curve的半高寬值為0.125°，並以ψ-scan量測確定AlN/GaN/Sapphire三層結構之間磊晶成長的關係；另外我們也成功的證實AlN/GaN異質結構能感應出二維電子氣，使其片載子濃度能達到-1.24×1013cm-2。此結果對將來製作以AlN/GaN異質結構為基礎的MISFET等高功率元件，將有所貢獻。

關鍵字

低溫成長 ； 二維電子氣 ； 氮化鎵 ； 磊晶成長 ； 氮化鋁 ； 迴旋濺鍍系統

並列摘要

AlGaN/GaN heterostructure field-effect transistors (HFETs) have been a subject of intensive investigation recently and have emerged as attractive candidates for high voltage, high-power operation at microwave frequencies such as low noise microwave amplifier, power microwave amplifier, high temperature devices and power suppliers. However, there exist some problems. One of those is large lattice mismatch as increasing the Al content, which increases the defects of interface and decreases the sheet carrier concentration as well as the carrier mobility.
Therefore some research groups suggested to use the AlN/GaN heterostructure. AlN/GaN heterostructure would have much higher sheet carrier concentration, if the difficulties of deposition can be overcome. The aims of this study are to deposit epitaxial AlN films on GaN/Sapphire substrates at low growth temperature, and investigate the presence of large polarization field in the AlN barrier layer which results in high values of the 2DEG sheet density.
Epitaxial AlN films have been successfully deposited on GaN/Sapphire substrates at low-temperature (300℃) using Helicon sputtering system. The FWHM of XRD rocking curve for (002) peak of AlN film is 0.125 and the scan confirms the epitaxial orientation relationship between the three layers of AlN/GaN/Sapphire. The two dimensional electron gas induced by AlN/GaN heterojunction has been measured to achieve -1.24×1013cm-2. The fruitful results will have contributions for fabricating high-power devices based on AlN/GaN heterojunction.

並列關鍵字

2DEG ； AlN ； epitaxial growth ； low temperature deposition ； GaN ； Helicon sputtering system

參考文獻

Caracas Conference on Devices, Circuits and Systems, Aruba, April 17-19, (2002).

157, (2002).

5. O. Ambacher, B. Foutz, J. Smart, J.R. Shealy, N.G. Weimann, K.

Fini, E. Haus, S.P. Denbaars, J.S. Speck and U.K. Mishra, Jorunal of Applied Physics, Vol 86, 4520, (1999).

Electron Devices, Vol 48, 450, (2001).