CS Online reports: Sumitomo Electric (SEI) said it has developed a mass production technology for 2-inch semi-polar/non-polar GaN substrate materials used as substrates for green lasers and as white LED substrates.
For white LEDs and blue-violet or blue semiconductor laser diodes, the c-plane of the GaN substrate is generally used as the growth crystal plane. However, since the positively charged gallium (Ga) and the negatively charged nitrogen (N) have alternating atomic structures, the c-plane exhibits a strong polarity, thereby reducing the efficiency of the illuminant in the green region.
Since the development of green semiconductor lasers in 2009, SEI has been developing nano- and non-polar GaN substrates (rather than polar c-plane GaN), which can improve the performance of green and white LEDs. After efforts to develop, the manufacturing technology effectively suppresses the polarization effect on the polar substrate material, thereby improving the luminous efficiency of the device.
The SEI indicates that, in general, semi-polar and non-polar GaN substrates are obtained by cutting vertically or diagonally along the c-plane orientation. However, this method is only for crystals with relatively small crystals (rectangular crystals with a size of only a few microns); such a small size is a major obstacle to increasing the yield of high-efficiency LED devices.
To overcome this bottleneck, SEI introduced HVPE manufacturing technology for mass production of 2-inch substrates. SEI said that substrates produced using HVPE fabrication technology have a dislocation density on the order of 105, which is comparable to the widely used c-plane substrate values ​​today.
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