氧化鋅鎵之透明導電薄膜材料特性與其應用在氮化鎵發光二極體上之研究

Investigation of Ga-doped ZnO Transparent Conducting Thin Films Deposited by Electron Beam Evaporation Technique on GaN-based Blue Light Emitting Diode

葉智禮(Chi-Li YEH)

指導教授 ： 郭政煌

國立中央大學/理學院/光電科學研究所/碩士(2008年)

摘要

本論文採用電子槍蒸鍍系統，蒸鍍透明導電薄膜GZO，探討薄膜光電特性與材料特性，以及在P型氮化鎵上歐姆接觸，最後應用在氮化鎵LED上與傳統薄膜ITO相互比較，探討其光電特性。
當Ga在薄膜GZO的含量約為6 At%時，薄膜電阻率可達最低值為2.44 ×10-4 ohm-cm。薄膜GZO與傳統薄膜ITO相比，薄膜電阻率同在1×10-4 ohm -cm 等級，在可見光波段皆具有90%的穿透率。
蒸鍍兩組不同電阻率的薄膜GZO在P型氮化鎵上與氮化鎵LED晶片上，與傳統之透明導電薄膜ITO相互比較，樣品P-1 = 6.31×10-4 ohm-cm和P-2 = 3.56×10-4 ohm -cm 分別為薄膜GZO在P型氮化鎵上的薄膜電阻率與樣品P-ITO = 1.73× 10-4 ohm -cm為薄膜ITO在P型氮化鎵上的薄膜電阻率，其特徵接觸電阻值為P-1 = 7.49×10-1 ohm-cm2、P-2 = 1.48×10-1 ohm-cm2和P-ITO = 2.61 ×10-2 ohm-cm2。在20mA電流注入下的操作電壓值，GZO LED -1= 3.89 V和GZO LED-2 = 3.47 V比ITO LED = 3.35 V分別高出約 0.54V和0.12V。在20mA電流注入下之光輸出功率值，GZO LED-1=2.02 mW和GZO LED-2= 1.98 mW比ITO LED = 1.7 mW分別約高出19%和16%，在20mA 電流注入下之外部量子效率值，GZO LED-1=3.63%和GZO LED-2 = 3.55%比ITO LED 3.06%分別約高出18.6%和16%。
另外，薄膜GZO在不同溫度熱處理後，薄膜的電阻率皆變大，且薄膜GZO在P型氮化鎵上的特徵接觸電阻值皆變大。在20mA 電流注入下，經不同溫度熱處理後之GZO LED其操作電壓皆變高，且在光輸出功率和外部量子效率值都變小。

關鍵字

氧化鋅鎵 ； 電子槍 ； 氮化鎵發光二極體

並列摘要

In this study, we adopt E-Gun evaporation system to deposit Gallium doped Zinc Oxide (GZO). We analyze the optical and electrical properties of GZO thin film and also discuss the contact property on p-GaN. Finally, we compare the electrical and optical characteristics of GZO TCL LEDs with conventional ITO TCL LEDs.
At the Ga content of 6At.%, we obtained the lowest resistivity (ρ) was 2.44×10-4 ohm-cm which was at the same order of ITO thin film (1×10-4 ohm-cm) and the transmittance was the above 90% at visible range which was comparable with ITO thin film. We prepared two as-deposited GZO films on p-GaN and LEDs of different resistivities, 6.31×10-4 ohm-cm (P-1) and 3.56×10-4 ohm-cm (P-2), to study the electrical contact property and compared with ITO film with resistivity of 1.73×10-4 ohm-cm (P-ITO). The specific contact resistances (ρc) of P-1, P-2 and P-ITO were 7.49×10-1 ohm-cm2, 1.48×10-1 ohm-cm2 and 2.61 ×10-2 ohm-cm2, respectively. After the chip process, we characterized the electrical and optical properties of GZO-LEDs and ITO-LEDs at the injection current of 20mA. The forward voltage of GZO LED-1, GZO LED-1 and ITO-LED were 3.89 V, 3.47 V and 3.35 V, respectively. The forward voltage of GZO-LEDs exhibited 0.54V and 0.12V higher than that of ITO-LED. The output powers were 2.02mW, 1.98mW, and 1.7mW for GZO LED-1, GZO LED-2 and ITO LED, respectively. The output powers were enhanced by 19% and 16% for GZO LED-1, GZO LED-2 compared with that of ITO-LED. On the other hand, the external quantum efficiency were 3.63% and 3.55% for GZO LED-1, GZO LED-2 which showed 18.6% and 16% enhancement compared with that of ITO-LED,3.06%. We also did annealing process for GZO films and then did the chip process. However, we found that? ρ and ρc would be deteriorated after annealing process. At 20mA injection current, the forward voltages were higher than those as-deposit and degradations of EQE and output powers were also observed.

並列關鍵字

GZO ； E Beam ； GaN LED

參考文獻

1. C. H. Kuo, H. C. Feng, C. W. Kuo, and C. M. Chen, L. W. Wu, G. C. Chi “Nitride-based near-ultraviolet light emitting diodes with meshed p-GaN”, Appl. Phys. Lett. 90 ,142115 (2007)

2. Chul Huh, Kug-Seung Lee, Eun-Jeong Kang, and Seong-Ju Park “Improved light-output and electrical performance of InGaN-based light-emitting diode by microroughening of the p-GaN surface”, J. Appl. Phys. 93, 9383 (2003)

3. Chi-Ling Lee and Wei-I Lee “Effects of strained InGaN interlayer on contact resistance between p-GaN and indium tin oxide”, Appl. Phys. Lett. 90, 181125 (2007)

4. S. W. Chae, K. C. Kim, D. H. Kim, T. G. Kim, S. K. Yoon, B. W. Oh, D. S. Kim,and H. K. Kim “Highly transparent and low-resistant ZnNi/indium tin oxide Ohmic contact on p-type GaN”, Appl. Phys. Lett. 90, 181101 (2007)

5. Sung-Pyo Jung, Denise Ullery, Chien-Hung Lin, Henry P. Lee, Jae-Hong Lim, Dae-Kue Hwang, Ja-Yeon Kim, Eun-Jeong Yang, and Seong-Ju Park “High-performance GaN-based light-emitting diode using high-transparency Ni/Au/Al-doped ZnO composite contacts” , Appl. Phys. Lett. 87, 181107 (2005)