本實驗提出一個利用氧化閘極金屬來縮短有效的閘極長度方法。氧化方式提供了快速、方便、成本低且有效提升元件特性。使用氧化閘極金屬製程是利用了各個金屬有各別不同的氧化係數，且氮化鎵(GaN)具有優異的化學穩定性和物理穩定性，不易受雙氧水氧化所影響。當元件閘極金屬製作完成後，利用一般雙氧水使元件閘極金屬氧化，因閘極金屬鎳/金的氧化能力不同，導致閘極下方金屬有效縮短長度。實驗結果顯示，經氧化處理後改善元件的直流和微波特性:飽和電流密度IDSS0 (305 mA/mm -> 322 mA/mm) 、最大轉導值gm,max (99 mS/mm -> 114 mS/mm)、夾止電壓Vpinch-off (–3.2 V -> –3 V)、電流增益截止頻率fT (11.1 GHz -> 14.4 GHz)、最大震盪頻率fmax (14.6 GHz -> 17.4 GHz)、最小雜訊NFmin (1.902 dB -> 1.384 dB)，最大輸出功率Pout (24.5 % -> 31.1 %) 。

In this work, we preset an effective method of shrinking gate length by oxidization gate metal. The oxidization method’s advantages are fast, low cost, simple and effective increase devices performance. The gate metal process to be use metal different coefficient of oxidization by oxidization treatment, and the GaN has excellent chemical and physics stability, so it is difficult to be oxidized by the H2O2. We can oxidize the gate metal by using general H2O2 after we finish the gate metal’s process. Because the different coefficient of oxidization of Ni/Au gate meal, it is effective to shrink gate length of metal below the gate.Experiment results indicate that the oxidization process can improve devices DC and microwave characteristics: the saturation drain current density IDSS0 (305mA/mm -> 322 mA/mm), the maximum extrinsic transconductance gm,max (99 mS/mm -> 114mS/mm), the pinch-off voltage Vpinch-off (–3.2 V -> –3 V), the unity current gain cut-off frequency fT (11.1 GHz -> 14.4 GHz), the maximum oscillation frequency fmax (14.6 GHz -> 17.4 GHz), the minimum noise figure NFmin (1.902 dB -> 1.384 dB) and the power-added-efficiency (P.A.E.) (24.5 % -> 31.1 %).

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