高頻氮化鋁鎵/氮化鎵高電子遷移率晶體之研究

Abstract

本篇論文中，我們採用於高阻矽基板上的氮化鋁鎵/氮化鎵異質接面結構製作高頻HEMT元件，並分析其直流與高頻特性。 論文首先針對元件的直流特性進行分析，我們利用電子束技術成功製作出閘極線寬150奈米的元件，最高將gm推至247.4 mS/mm，並針對不同的幾何尺寸進行探討 接著為了分析元件的高頻特性，我們利用ADS模擬軟件建立一套小訊號等效電路模型，幫助我們了解元件內部小訊號參數的影響，同時也針對不同幾何尺寸的元件進行分析，最佳元件fT與fmax於汲極偏壓30V下，分別為25.86 GHz和99.26 GHz。 最後為了進一步提升截止頻率，我們開發T型閘極製程，其目的為降低Rg電阻，使fmax能繼續往上提升。

In this thesis, we fabricate the RF device with AlGaN/GaN heterostructures on 4-inch silicon substrate and analyze their electrical characteristics. First, we analyze the DC chatacteristics of device. We successfully use E-beam lithography technology to define gate length about 150nm. The small gate length leads high transconductance(gm) about 247.4 mS/mm. We also discuss different geometric device in this part. For high frequency characteristics, we build the small-signal model by ADS and simulate each component in the circuit. The best device fT and fmax are 25.26GHz and 99.26 GHz respectively in VD=30V. Finally, in order to push up the fmax value, we develope the T-shaped gate process. In this structure, the wide upper layer increases the croess-sectional area of the gate, thus reducing gate resistance.