室溫兆赫波物理、元件與技術(I)

Abstract

近年來有關兆赫波科技的相關研究日益增多。由於兆赫波(頻率約1~10 THz， 介於可見光與微波波段之間)有著許多可見光與微波所沒有的特性(如：能靈敏偵測 水分子的含量變化、可穿透可見光無法穿透的物體等)，因此兆赫波量測技術被大 量地研究與應用於許多不同領域，諸如：生醫顯像、半導體製程檢測、太空遙測、 國安防恐、食物品管等。種種應用都建構在有優良可靠的兆赫波輻射源基礎上。本 計畫將致力於室溫兆赫波光源之製作、量測、製程技術之建立與相關元件物理特性 之了解及探討。有別於透過居量反轉機制所產生的雷射或非線性光學所產生之輻 射， 本研究將由固態電子震盪器的角度出發， 透過結合電子波共振機制 (Dyakonov–Shur instability)與次微米乃至深次微米的前瞻製程，製作能夠在室 溫下操作的半導體兆赫波輻射元件。由於不同的材料系統與元件操作頻率息息相 關，我們將同時針對三種熱門的三五族系統（GaAs、InP 與ＧaN 的高遷移率場效電 晶體）先做製程上技術之建立，進而製作比目前Gunn diode(約300 GHz)、IMPATT diode(約400 GHz)或Resonant tunneling diode(約1 THz)還要高頻的兆赫波震盪 輻射元件。為了解元件特性，除了量測元件的高頻參數外，將利用傅立葉轉換紅外 光譜儀對元件輻射頻譜進行量測與分析，最終並製作陣列元件以提升元件輻射性 能。

The research interests on the applications of the terahertz (THz) technology have been keeping increasing in recent years. Compared with the visible lights and the microwaves, the THz waves (1 – 10 THz) have lots of unique properties (For example, they are sensitive to the water content in the materials and are able to penetrate through most of the insulating materials, etc.). Due to these properties, the THz measurement techniques are used for biomedical imaging, process inspection for semiconductor industry, astronomy, homeland security, food quality control, etc. All these applications rely on highly reliable THz emission sources. The project will focus not only on manufacturing the room-temperature THz emitting devices but also investigating the physics behind these devices. Instead of building photonic devices, we will investigate the electronic oscillators based on a different kind of oscillating mechanism: Dyakonov–Shur instability. We will build up techniques for manufacturing the high mobility field effect transistors with sub-micron or deep sub-micron gate length on three types of systems: GaAs, InP, and GaN. Oscillators with oscillating frequencies much higher than the IMPATT, Gunn, or RTD diodes will be fabricated and investigated. Not only the high frequency parameters of these devices will be obtained but also the radiation spectra will be measured and analyzed. Finally, HEMT arrays will be fabricated for emission power enhancement.