高崩潰電壓氮化鋁鎵/氮化鎵蕭基二極體之特性分析 ; Analysis of AlGaN/GaN High Breakdown Voltage Schottky Diodes

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Title:	高崩潰電壓氮化鋁鎵/氮化鎵蕭基二極體之特性分析;Analysis of AlGaN/GaN High Breakdown Voltage Schottky Diodes
Authors:	林佩瑩;Pei-ying Lin
Contributors:	電機工程研究所
Keywords:	漏電流;Schottky diode;leakage current
Date:	2010-08-31
Issue Date:	2010-12-09 13:55:40 (UTC+8)
Publisher:	國立中央大學
Abstract:	文中，我們分別於高阻值氮化鋁及傳統氮化鎵兩種緩衝層上成長氮化鋁鎵/氮化鎵異質結構，並製作平面式蕭基二極體。元件量測結果顯示具高阻值氮化鋁緩衝層之元件可大幅提升其崩潰電壓，並同時維持低漏電流密度。所以，在此研究中我們深入探討不同緩衝層對蕭基二極體特性差異的因素並分析其漏電流機制。在材料品質分析方面，從x-ray繞射量測GaN(002)繞射轉動曲線中，顯示出氮化鋁緩衝層可有效地降低磊晶材料的螺旋差排密度以減少漏電流路徑。而從蝕刻孔洞密度缺陷(Etching pits density, EPD)量測中，亦計算出氮化鋁緩衝層能有效降低上方磊晶結構之差排缺陷密度至3.2×107 cm-2，相較於具氮化鎵緩衝層之結構約降低了一個數量級左右。在漏電流分析方面，我們分別針對緩衝層漏電流與氮化鋁鎵位障層漏電流兩個部分進行討論。其中氮化鋁緩衝層之阻值比氮化鎵緩衝層阻值大了六個數量級左右，顯示出氮化鋁緩衝層具有極低的漏電流特性；此外，我們利用變溫電流-電壓量測與變頻電容-電壓量測分析漏電流機制，發現在電壓為0 V~-6 V下的漏電流來源主要為氮化鋁鎵位障層，而在小於-6 V偏壓下的漏電流行為則由緩衝層品質主導，再以夫倫克爾-普爾發射(Frenkel–Poole emission, F-P emission)的漏電流模型計算出各試片氮化鋁鎵中的缺陷能階。In this study, AlGaN / GaN HEMT structures on the high-resistance AlN buffer layer and the conventional GaN buffer layer were grown, respectively. The planar Schottky diodes were then fabricated on these structures. From the I-V measurement, the results indicate the device with high-resistance AlN buffer layer not only substantially promote the breakdown voltage but also keep the low leakage current density. Therefore, in this study we discussed in detail about the factors of SBDs characteristics on different buffer layers, and further analyzed the mechanism of leakage current. In the analysis of material quality, according to the x-ray diffraction GaN (002) rocking curve shows that AlN buffer layer can effectively reduce the screw-type dislocation density of epitaxial materials, thus reducing the leakage current. Besides, the etching pits density (EPD) is also calculated that the dislocation density of the above epitaxial structure reduced to about 3.2x107 cm-2, which is about an order lower compared to the epitaxial material grown on the GaN buffer layer. In the analysis of leakage current, the leakage current in the buffer layer and the AlGaN barrier layer are discussed, respectively. In the discussion, the resistance of the AlN buffer layer is about six orders greater than that of the GaN buffer layer, indicating that the AlN buffer layer has the characteristic of low-leakage current; in addition, temperature-dependent current-voltage (I-V) measurement and frequency-dependent capacitance-voltage (C-V) measurement are used to analyze the mechanism of leakage current. The results show that the primary source for the leakage current during the voltage of 0 V~ - 6 V is the AlGaN barrier layer while the leakage current is dominated by the quality of buffer layer below -6 V. To further discussion, defect energy levels in AlGaN barrier are quantified by the leakage current model of Frenkel-Poole emission (F-P emission).
Appears in Collections:	[Graduate Institute of Electrical Engineering] Electronic Thesis & Dissertation

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