Blue Optoelectronics in III-V Nitrides on Silicon

Three simple and promising methods to grow high-quality, device-relevant gallium nitride heterostructures on silicon are presented: strain-compensation, patterning, and the insertion of low-temperature AlN interlayers. With all methods device-quality GaN can be grown. While patterning is especially interesting for light emitters, low-temperature AlN interlayers can be used universally not only for transistor structures, which require good insulation of the active layers to the Si substrate, but also for vertically contacted LEDs when doped with Si. Low-temperature AlN interlayers do not only reduce tensile stress but also improve GaN properties and strongly reduce the threading dislocation density from 10$\text{}^{10}$ cm$\text{}^{-2}$ to 10$\text{}^{9}$ cm$\text{}^{-2}$ for 2 low-temperature AlN layers. Additionally, the layer quality can be enhanced by using in situ Si$\text{}_{x}$N$\text{}_{y}$ masks. Best crack-free layers with dislocation densities around 10$\text{}^{9}$ cm$\text{}^{-2}$ show X-ray rocking-curve widths around 400 arcsec and narrow photoluminescence. So far, best LEDs on Si(111) have an optical output power of 0.42 mW at 20 mA and 498 nm which is enough for simple signal applications.