具有氧化物閘極介電層之氮化鎵/氮化鋁鎵： 金屬-氧化物-半導體閘極結構之高電子遷移率電晶體

Abstract

本次專題藉由超音波霧化熱裂解沉積研製具有氧化鎂閘極介電層之氮化鎵/氮化鋁鎵/氮化鎵金屬-氧化物-半導體閘極結構之高電子遷移率電晶體。由於利用超音波霧化熱裂解沉積高介電常數氧化鎂當閘極介電層，因而增強閘極絕緣能力與表面鈍化效果，進而有效地降低閘極漏電流。 經由製程最佳化條件下之傳統蕭特基閘極與氧化鎂閘極介電層之氮化鎵/氮化鋁鎵/氮化鎵金屬-氧化物-半導體閘極結構之高電子遷移率電晶體，元件之直流特性分別為: 最大飽和電流密度 IDS, max (500 mA/mm、681 mA/mm)，零閘極偏壓飽和電流 IDSS0 (289 mA/m、329 mA/mm)，最大外質轉導 gm, max (120 mS/mm、112 mS/mm)，閘極漏電流 Ig (6.85 × 10-3 mA/mm、3.73 × 10-5 mA/mm)，閘極-汲極兩端崩潰電壓 BVGD (-104 V、-123 V)。 因此，實驗結果顯示，藉由超音波霧化熱裂解沉積高介電常數氧化鎂閘極介電層結構之氮化鎵/氮化鋁鎵/氮化鎵高電子遷移率電晶體，成功改善元件整體之直流特性。

The thesis investigates MgO-dielectric GaN/AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) by using the ultrasonic spray pyrolysis deposition (USPD) technique. Due to the enhanced gate insulation and surface passivation, the gate leakage current has been effectively reduced by depositing the high-k magnesium dioxide (MgO) as the gate dielectric layer. Improved device performances of the studied MgO-dielectric MOS-HEMT (a referenced Schottky-gate HEMT) have been achieved, including maximum drain-source saturation current density (IDS, max) of 681 (500) mA/mm, drain-source current density at VGS = 0 V (IDSS0) of 329 (289) mA/mm, maximum extrinsic transconductance (gm, max) of 112 (120) mS/mm, reduced gate leakage current (Ig) at VGS = -50 V of 3.73 × 10-5 (6.85 × 10-3) mA/mm, and two-terminal off-state gate-drain breakdown voltage (BVGD) of -123 (-104) V, respectively, at 300 K. Consequently, superior performance of the present MOS-HEMT has been successfully achieved in this thesis. High-k MgO MOS-gate structure has been obtained by using the cost-effective USPD technique. The present MOS-HEMT device can be promisingly applied to high-frequency RFIC technologies.