| Semiconductor light-emitting diode (Light Emitting Diode), referred to as LED, is the electroluminescent device which transfer electrical energy into light energy. LED light source has features like a small size, low power, to better reflect the true color of the illuminated object, long life, high brightness,low-calorie, durable, safe and environmentally friendly, so applications of LED in the lighting field are very broad. As people learn more and more about LED, its application has become more widely used, for example, applications in the indicator and the display backlight. Preparing an LED device, P-GaN is the out-light layer, there is a deposition layer of metal as a conductive electrode on its top. Since the carrier concentration of the semiconductor material is low, and the electrical conductivity is poor, the current can not scale well, which limiting the efficiency of the light. Therefore, in order to improve the light efficiency, there need a film material which has both good conductivity and good light-transmissive between the light-layer and the electrode to ensure the light generated in the active region can be revealed uniform. Indium tin oxide (Indium Tin Oxide), referred to ITO, is a heavily doped n-type high-degenerate semiconductor. It also has a high visible light transmittance and conductivity. Other advantages of ITO films are also very prominent, such as chemical stability, high thermal stability, while having good adhesion to the substrate, and the ease of graphics processing. Due to the excellent properties of ITO films, it has been very widely used in the semiconductor optoelectronic devices, such as displays and solar cells applications,it has become an integral part used as a current spreading layer in the LED device. Depending on the preparation of principles, the preparation of ITO thin film mainly divided into two major categories of chemical and physical methods. Among them, chemical methods include sol-gel, spray pyrolysis, homogeneous precipitation method and chemical vapor deposition; physical methods include evaporation deposition, pulsed laser deposition (PLD) and magnetron sputtering.The ITO thin film was prepared by magnetron sputtering film progresses in this experiment. The target is (90wt%In2O3+10wt%SnO2) of ITO ceramic target. The film sheet resistance was tested by a four probe instrument. The transmittance was tested by UV-visible spectrophotometer. The film thickness was tested by step apparatus. In the experiment we changed the O2flow, sputtering power, pressure and deposition temperature to study the influence on the transmittance of the sheet resistance of the ITO film, then we analyzed and explained the reasons for its influence. We got a set of ITO films which has ideal optical properties in the experiments in O2flow0.2sccm, Ar flow80sccm, the sputtering power is260W, the deposition pressure is2.0mTorr, deposition temperature is35℃, the film thickness is120nm. The sheet resistance is29.2Ω/sq, visible light (wavelength455nm) transmittance is99.3%. |
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