Back Cover: Study of defects and lifetime of green InGaN laser diodes (Phys. Status Solidi A 3/2012)



original image

InGaN quantum wells for direct green lasers with indium concentrations of about 30% are studied by Uwe Strauss and co-workers (pp. 481–486) in respect to defect structure and influence of defects on device lifetime. A new test structure enables them to determine strain relaxation in In-rich layers by X-ray diffraction even at typical well thicknesses of few nanometers. The cover shows reciprocal space maps of such a test structure including quantum wells for green lasers and a reference structure, respectively. The authors describe that there is a high risk to generate screw and edge dislocations in the In-rich quantum wells in non-optimized structures as verified by transmission electron microscopy. Such defects strongly influence the device lifetime of green lasers. Optimized active layers already enable stable operation over a period of more than 1000 hours at 50 mW constant power at 517 nm emission wavelength with an extrapolated increase of operation current by less than 30% within this time.