電子槍蒸鍍氧化銦錫薄膜在AlGaInP發光二極體應用之研究

Study of E-gun evaporated ITO thin film on application of AlGaInP light emitting diode

劉建成(Chien-Cheng Liu)

指導教授 ： 廖森茂 ； 吳志宏

中原大學/工學院/電子工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400147

摘要

氧化銦錫(Indium-Tin Oxide, ITO)對可見光具高度透明度及電傳導性，常當做一個透明電極 ，被廣泛地使用在發光元件上。在本研究中，使用快速熱退火(RTA)的熱處理方式，並以圖一的元件結構，來探討ITO經熱處理後對AlGaInP紅光二極體的影響。
首先，我們用電子束個別蒸鍍兩種不同比例(In2O3/SnO2=90/10 or 95/5)ITO於p+-GaAs基板、半絕緣GaAs基板與玻璃上，並以快速熱退火分別通入氮氣(N2)及氫氣(H2)做熱處理，通入H2做熱處理的ITO薄膜，從特徵接觸電阻與霍爾量測，顯示具有較低的特徵接觸電阻與片電阻，但是透光度卻相當差；而以N2做熱處理的ITO薄膜經由最佳的熱處理會有較高的氧含量，並因為N2的導入ITO內導致高的透光度(＞90%)。此外，ITO蒸鍍靶材成分的不同也影響其光和電的特性，我們發現ITO(In/Sn=90/10)經過熱處理有較好的電特性而ITO(In/Sn=95/5)有較好的光特性。
在ITO薄膜的光電特性量測之後，蒸鍍ITO在AlGaInP紅光二
極體上當作電流分散層(current spreading layer)及優良的光取出界面。由於ITO 與GaAs的低特徵阻值(約1~5×10-4Ω-cm2)和在可見光光譜範圍的高穿透率被成功地應用在LED的製作上。我們發現有加ITO的LED有較好的I-V特性和較小的半高波寬，此外當ITO厚度為50nm在氮氣中(N2)及溫度400oC以上回火可以得到比一般沒加ITO的LED更高的光輸出功率，確信能改善目前在市場上之發光二極體。

關鍵字

氧化銦錫 ； 發光二極體 ； 電子槍

並列摘要

Indium tin oxide (ITO) that has unique characteristics of good conductivity and high light transmission over the visible spectrum is the most widely used as the transparent conducting electrode to the applications of optoelectronic devices. This thesis will employ rapid thermal annealing (RTA) process to investigate the characteristics and the performance of ITO films on AlGaInP light emitting diodes (LEDs). The main device structure is shown schematically in Fig.1.
First, ITO was individually deposited on p+-GaAs with concentration of about 1× 1019 cm-3 、semi-insulated GaAs and glass substrates by E-beam evaporation method. ITO disks were bombarded by two kind of In2O3/SnO2 composition ratios (90/10 or 95/5) employed as a target. ITO films were treated using RTA in the hydrogen and nitrogen ambient, respectively. After annealing in the H2 ambient, the lower specific contact resistivity ρc and sheet resistivity Rsh were obtained, but the transmittance of ITO films were even low. In the N2 ambient, a high transmittance more than 90% was obtained, because of the introduction of oxides. Besides, different ratios of ITO target also influence the optical and electrical characteristics. ITO films (In/Sn=90/10) exhibited better electrical characteristics and ITO films (In/Sn=95/5) present better optical characteristics.
After the measurements of the optical and electrical characteristics, evaporated transparent conducting Indium-tin oxide (ITO) layers are

utilized as the window material and the current spreading layer on AlGaInP light emitting diodes (LEDs). ITO films of thickness 50nm revealed the specific contact resistivity ρc of about 1~5×10-4Ω-cm2 and the transmittance of up to 90% in the visible spectral region, which were used for AlGaInP light emitting diodes (LEDs). It can be seen that ITO-coating LEDs demonstrate better I-V characteristics and smaller full width at half maximum (FWHM) than LEDs without ITO. Besides the devices incorporated with the ITO layer annealed in the N2 ambient above 400oC give a marginally greater output than the conventional non-ITO devices. It was suggested that the developed typical process will improve nowadays commercial LEDs.

並列關鍵字

AlGaInP light emitting diode ； ITO ； E-gun

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