Developing nitride-based blue LEDs on SiC substrates

Blue light-emitting diodes (LEDs) have consistently increased in brightness as devices have evolved from the homojunction SiC device to the double heterojunction GaN-based LED on SiC substrates. These LEDs are used in a wide range of applications requiring blue, white, and/or a combination of colors. The technology to develop the nitride devices involves growing single-crystal thin films with compositions from AlN-InN-GaN via metalorganic chemical vapor deposition on single-crystal 6H-Sic substrates. In this study, AlGaN containing high and low fractions of aluminum was grown directly on the SiC for use as a buffer layer. Subsequent epitaxial layers of GaN and AlGaN were doped with magnesium and silicon to achieve p-type and n-type conductivity, respectively. N-type InGaN layers with indium compositions up to ∼50% were also achieved.