Technological problems of epitaxial wafer and LED chip

1. epitaxial wafer refers to a semiconductor thin film grown on a substrate, which is mainly composed of three parts: p-type, quantum well and n-type. At present, the mainstream epitaxial material is gallium nitride (GaN), and the substrate materials are mainly sapphire, silicon and silicon carbide. Generally, there are five quantum wells. The commonly used production process is MOCVD. This is the core part of the LED industry, with high technical requirements and large capital investment (usually tens of millions for one MOCVD).

2. The detection of epitaxial wafer is generally divided into two categories:

1. Optical performance test. The main parameters include working voltage, light intensity, wavelength range, half-peak width, color temperature and color rendering index. These data can be tested by integrating spheres.

The second is reliability test, the main parameters include light attenuation, leakage, back pressure, antistatic, I-V curve and so on. These data are generally tested by aging.

3. It should be pointed out that there is no white LED chip, only white LED lamp beads/tubes, that is, packaging is needed to obtain small white LED lamps, which are also commonly known as lamp beads and tubes.

White LED is generally obtained in two ways:

Firstly, the red, green and blue chips are packaged in proportion by light distribution, and a white LED is obtained.

Second, the blue LED is converted by the phosphor, thereby obtaining the white LED.

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