銀/鈀/銅合金反射式電極 於紫外光發光二極體之研究

Abstract

本篇論文主要是研究將反射式電極(鉻/銀合金/鉻/金)在紫外光發光二極體元件上之光電特性差異，藉以反射式電極(鉻/銀合金/鉻/金)其相較於傳統電極(鉻/金)能具有高反射率值，使其應用在紫外光發光二極體元件上時能具有高的光輸出功率及功率轉換效率，並將反射式電極條件(鉻/銀合金/鉻/金)分別在N-AlGaN上及在ITO/P+-GaN/P-AlGaN上時能分析其特徵接觸電阻值特性，應用在更短波長之紫外光發光二極體元件時，能夠更有效的降低元件整體之串聯電阻，進而使元件有低的導通電壓。 首先，由量測反射率部份可得知，於386nm波段處其反射式電極鉻/銀合金/鉻/金(20Å/600Å/500Å/800Å)的反射率值為65.7%相較於傳統電極鉻/金(500/800Å)的反射率為38.2%，另外，368nm波段處其反射式電極鉻/銀合金/鉻/金(20Å/600Å/500Å/800Å)的反射率值為61.8%相較於傳統電極鉻/金(500/800Å)的反射率為38.0%。 接著探討反射式電極(鉻/銀合金/鉻/金)在紫外光發光二極體元件上之光電特性研究。386nm紫外光發光二極體，於操作電流為20mA時，在反射式電極的條件為鉻/銀合金/鉻/金(20Å/600Å/500Å/800Å)及鉻/金(500Å/800Å)時，所對應的串聯電阻與導通電壓分別為17.90Ω、16.89Ω與3.51V、3.47V，並且所對應的光輸出功率與功率轉換效率分別為29.32mW、26.54mW與41.77%、38.24%，其光輸出功率與功率轉換效率相較於傳統電極鉻/金(500Å/800Å)，分別提升了10.5%、9.2%; 而368nm紫外光發光二極體，於操作電流為20mA時，在反射式電極的條件為鉻/銀合金/鉻/金(20Å/600Å/500Å/800Å)以及鉻/金(500Å/800Å)時，所對應的串聯電組與導通電壓分別為34.87Ω、34.45Ω與4.02V、3.99V，並且所對應的光輸出功率與功率轉換效率分別為1.09mW、1.01mW與1.36%、1.27%，其光輸出功率與功率轉換效率相較於傳統電極鉻/金(500Å/800Å)，分別提升為7.9%、7.1%。 最後探討反射式電極(鉻/銀合金/鉻/金)分別在N-AlGaN上以及在ITO/P+-GaN/P-AlGaN上之歐姆接觸特性研究。反射式電極鉻/銀合金/鉻/金(20Å/600Å/500Å/800Å)以及傳統電極鉻/金(500Å/800Å)時，分別於N-Al0.04Ga0.96N上其特徵接觸電阻值分別為2.19×10-4Ω-cm2、9.71×10-3Ω-cm2，於ITO/P+-GaN/P-Al0.11Ga0.89N上其特徵接觸電阻值分別為1.01Ω-cm2、7.32Ω-cm2，顯示出以反射式電極鉻/銀合金/鉻/金(20Å/600Å/500Å/800Å)能夠有效地降低傳統電極(鉻/金)分別於N-AlGaN上以及ITO/P+-GaN/P-AlGaN上較低的特徵接觸電阻值。 綜合以上所述可歸納出以反射式電極鉻/銀合金/鉻/金(20Å/600Å/500Å/800Å)不僅有與傳統電極鉻/金(500Å/800Å)在紫外光發光二極體元件上較佳的串聯電阻與導通電壓之外，可以有效的提升紫外光發光二極體元件上光輸出功率輸出以及功率轉換效率，亦提供未來在深紫外光發光二極體之使用。

This paper mainly studies differences in the opticalelectrical characteristics of reflective metal pads (Cr/APC/Cr/Au) on ultraviolet light emitting diode(UV-LED) device. Reflective metal pads with Cr/APC/Cr/Au are expected to present a higher reflectance than those pads with Cr/Au. The former pads are also expected to have higher light output powers and wall plug efficiencies when used on ultraviolet light emitting diode device. Reflective metal pads with Cr/APC/Cr/Au further are believed to show a low specific contact resistance when they are used on N-AlGaN and ITO/P+-GaN/P-AlGaN. Therefore, their applications in deep UV-LED devices can effectively reduce the series resistance of the entire device, thereby causing the overall device to exhibit a decreased forward voltage. First, the measured reflectance reveals that the reflectance of Cr/APC/Cr (20 Å/600 Å/500 Å) at 386 nm is 65.7%. This reflectance is higher than that of Cr/Au (500 Å/800 Å), which is 38.2 %. Furthermore, the reflectance of Cr/APC/Cr (20 Å/600 Å/500 Å) at 368 nm is 61.8 %. This reflectance is higher than that of Cr/Au (500 Å/800 Å), which is 38.0 %. This paper then investigates the opticalelectric properties of the reflective metal pads (Cr/APC/Cr/Au) on UV-LED device. At an injection current of 20 mA and wavelength of 386 nm, the series resistances of reflective metal pads with Cr/APC/Cr/Au (20 Å/600 Å/500 Å/800 Å) and Cr/Au(500 Å/800 Å) are 17.90 and 16.89 Ω, their corresponding forward voltages are 3.51 and 3.47 V ,their light output powers are 29.32 and 26.54 mW, and their wall plug efficiencies are 41.77 %, and 38.24 %, respectively. Compared with those of the conventional pad Cr/Au (500 Å/800 Å), the light output powers of the reflective metal pads with Cr/APC/Cr/Au (20 Å/600 Å/500 Å/800 Å) and Cr/Au (500 Å/800 Å) increased by 10.5 %, and their corresponding wall plug efficiencies increased by 9.2 %. The corresponding series resistances of reflective metal pads with Cr/APC/Cr/Au (20 Å/600 Å/500 Å/800 Å) and Cr/Au (500 Å/800 Å) are 34.87 and 34.45 Ω, thier forward voltages are 4.02 and 3.99 V, thier light output powers are 1.09 and 1.01 mW, and their wall plug efficiencies are 1.36 %, and 1.27 %, respectively. Compared with those of the conventional pad Cr/Au (500 Å/800 Å), the light output powers of these pads increased by 7.9 %, and their corresponding wall plug efficiencies increased by 7.1 %. Finally, this paper investigates the ohmic contact properties of reflective metal pads Cr/APC/Cr/Au (20 Å/600 Å/500 Å/800 Å) on N-AlGaN and ITO/P+-GaN/P-AlGaN, The specific contact resistances of the reflective metal pads Cr/APC/Cr/Au (20 Å/600 Å/500 Å/800 Å) and the conventional pad Cr/Au (500 Å/800 Å) are 2.19×10-4 and 9.71×10-3 Ω-cm2 on N-Al0.04Ga0.96N and 1.01 and 7.32 Ω-cm2 on ITO/P+-GaN/P-Al0.11Ga0.89N, respectively. This finding shows that reflective metal pads with Cr/APC/Cr/Au (20 Å/600 Å/500 Å/800 Å) can more effectively reduce the higher specific contact resistances than the conventional pad Cr/Au on N-AlGaN and ITO/P+-GaN/P-AlGaN. In summary, reflective metal pads with Cr/APC/Cr/Au (20 Å/600 Å/500 Å/800 Å) exhibit not only better series resistances and forward voltages than the conventional pad Cr/Au (500 Å/800 Å) but also higher light output powers and wall plug efficiencies on UV-LED devices.This result reveals the future applications of deep UV-LED devices.