Samsung Advanced Institute of Science and Technology (SAIT) has developed a process to produce LEDs on 200 mm silicon. Using this platform instead of sapphire, the widely used substrate for making LEDs today, promises to cut the cost of LED deposition and processing.
A paper presented by SAIT at the ninth International Conference on Nitride Semiconductors (ICNS) described the method used to produce LED epi-structures with an internal quantum efficiency of 65 percent.
Growth of high-quality GaN layers on silicon is not easy, due to differences in both the lattice constant and the thermal coefficient of expansion of the two materials.
SAIT has addressed both these issues by creating a crack-free template featuring AlN/AlGaN buffer layers, intermediate layers and an n-type GaN layer.
On this template engineers have created an LED structure featuring five quantum wells and a p-type AlGaN electron blocking layer. Photoluminescence (PL) mapping of this epiwafer produced an average emission wavelength of 429.5 nm, with a standard deviation of 10.3 nm.
Temperature-dependent PL measurements suggest that the internal quantum efficiency of the LEDs is 65 percent.
The research team have also employed a substrate transfer technique to fabricate vertical-LED chips from 8-inch epiwafers.