由於鉬金屬與氮化鎵的線性熱膨脹係數非常接近，所以我們試著由鉬金屬去減少氮化鎵和銅基板之間的熱膨脹係數的差異。這次的研究中，將大約四微米的鉬-銅金屬導入氮化鎵和銅基板之間當作緩衝層，再利用這新的金屬基板完成垂直式發光二極體。我們研究不同鉬-銅的層數在經過熱壓力測試之後的變化。在氮化鎵表面現象上，觀察到在經過熱壓力測試過後銅基板有嚴重的破裂情形，相反的，擁有三對鉬-銅緩衝層的銅基板氮化鎵表面則是平滑無損。經過熱壓力測試，電性與光性量測上銅基板的漏電流增加67.7倍，而三對鉬-銅緩衝層銅基板結構有效的抑制漏電流的增加。銅基板光衰減了24.7%，三對鉬-銅緩衝層銅基板結構在光輸出特性的變化比銅基板來的更加穩定。

Due to the similar coefficients of thermal expansion (CTE) of molybdenum (Mo) and GaN, Mo was introduced to GaN and copper substrate to reduce the CTE mismatch. In this work, the molybdenum/copper layers were deposited about 4 μm as buffer layer between GaN and copper substrate for GaN-based vertical light emitting diodes (LEDs). Thermal effects on the GaN-based vertical LEDs with electroplating Cu substrate will be investigated. It is found that serious surface cracking of the LED with copper substrate only after thermal stress can be observed, on the contrary, GaN LED surface with 3 pair Mo/Cu buffer – Cu substrate is still smooth without the cracking behavior. As to the LED performance, the measured reverse current on Cu substrate was increased 67.7 times after thermal stress while effective suppressed in reverse current for the 3 pair Mo/Cu buffer – Cu substrate can be observed. In addition, 24.7% light output power reduction of Cu substrate was observed. The light output power for 3 pair Mo/Cu buffer – Cu substrate was more stable than that of Cu substrate only. It indicates that the Mo/Cu pairs can be effective to reduce the thermal effects for the GaN-based vertical LEDs on copper substrates.

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