Volker Haerle

Light extraction technologies for high efficiency GaInN-LED devices

Data are presented for an GaInN based thinfilm LED. The LED is fabricated by transferring the epilayers with laser lift off from sapphire to a GaAs host substrate. In combination with efficient surface roughening and highly reflective p-mirror metallisation an extraction efficiency of 70% and wall plug efficiency of 24% at 460nm have been shown. The chips showed 12mW @ 20mA with a Voltage of 3.2V. The technology is scalable from small size LEDs to high current Chips and is being transferred to mass production.

Nitride-based in-plane laser diodes with vertical currrent path

The realization of group III--nitride laser diodes with a vertical current path on a n-conducting SiC substrate is described. The vertical current path and the possibility of cleaved laser facets result in a simpler process technology. Gain spectra measured by the Hakki-Paoli method show a modulation of the modal gain due to parasitic modes in the SiC substrate. As up to now no defect reduction technique was successfully transfered to GaN on SiC, degradation is the major issue. We discuss the impact of degradation on the gain spectra, facet degradation, and rule out formation of cracks during degradation. We show that the high heat conductivity of SiC may give an advantage with respect to degradation as it results in a only moderate temperature rise of the active region.