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標題: 利用光輔助電化學技術製作具圖案化氧化鎵電流阻障層之氮化銦鎵發光二極體
InGaN Light Emitting Diodes with Patterned Gallium-Oxide Current Blocking Layer Through a Photoelectrochemical Process
作者: 曾王坡
Tseng, Wang-Po
關鍵字: 光輔助電化學
出版社: 材料科學與工程學系所
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摘要: 在本論文中,利用光輔助電化學(photoelectrochemical)氧化技術,在氮化鎵發光二極體平台區上製作圖案化的氧化鎵結構,由於鉻金電極之遮光效應造成光取出率下降,所以利用氧化鎵高電阻特性製作在P電極下方之電流阻障層,使電流注入透光ITO(銦錫氧化物)導電膜區域,可提升發光區注入電流密度並增加元件發光效率,最後對此元件之光、電特性加以探討。 經過多次氧化測試,發現光輔助電化學製程所生長的氧化鎵厚度與外加偏壓成正相關性,相同製程與時間下,電壓越大,氧化層越厚。而輸入電壓太大時氧化層會由底部側向氧化穿透我們所設計的光阻圖案;而輸入電壓太小則會無法使GaN氧化,實驗結果利用光輔助電化學技術,其溶液使用D.I. Water、輸入電壓DC 3V、氧化時間5~20 min是較適當的條件。5V以上光阻容易破壞無法有效形成圖案化氧化層;1V則無法有效進行氧化製程。 實驗結果發現,在P型金屬電極下方有製作圖案化氧化鎵當作電流阻礙層(current blocking layer,CBL)的元件,其發光強度較標準元件約提升29%;另外在透光ITO導電膜發光區下製作電流阻障層,雖可以加強其他區域電流密度,但卻因減少發光區域,最後發光強度不一定會上升,需要視氧化層區域與整體區域比例而定。
In this thesis,photoelectrochemical (PEC) techniques are utilized to fabricate patterned Gallium oxide(GaOx) structures in mesa region on GaN-based LED. The decrease of light extraction results in the cover effect of Cr/Au pad, so current blocking layer of Gallium oxide is fabricated under P pad for the higher electric resistant of Ga2O3. Then, the current injects into transparent ITO conduction layer so as to increase current density on active area and enhance lamination efficiency of device. By the way, the optical and electric characteristic of device are also investigated。 After several times test of oxidation, the thickness of Ga2O3 fabricated by PEC depends on the applied voltage. The larger voltage induces the thicker oxide thickness for the same process and time. When the input voltage is too high, the oxide will penetrate the photoresistant pattern by later oxidation form the bottom. On the other hand, when the input voltage is too slow, the oxidation is not performed. The optimization parameters in this experiment are to use the D.I. water as solution with 3V of applied voltage for 5-20 minute of the oxidation time. When applied voltage is higher than 5 V, the photoresistant is easily damaged and unable to form patterned oxidation effectively and the applied voltage is lower than 1V, the oxidation process is not carrier out。 According to the experimental results, the device with patterned current blocking layer of Gallium oxide under P pad, the lamination efficiency has 29% enhancement than standard LED. In addition, the current blocking layer fabricated under transparent ITO TCL can increase current density in other region, but the total light output intensity is not absolutely enhanced for the decrease of active area。
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