Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 64: GaN: Preparation and Characterization III

HL 64.1: Vortrag

Mittwoch, 28. März 2012, 16:30–16:45, EW 202

Overcoming the limiting factors to achieve green lasing — •Andreas Kruse, Uwe Rossow, and Andreas Hangleiter — Institut für Angewandte Physik, TU Braunschweig

Group-III nitrides based materials have attracted great interest for optoelectronic devices such as light emitting diodes (LEDs) and laser diodes (LDs). However, for long wavelength emitting LEDs and LDs many challenges need to be overcome to improve their device performance. We focus our study on investigations of limiting factors of optical gain in InGaN-based laser structures by extending the emission wavelength to the green spectral range. For this purpose we carry out optical gain measurements using the variable stripe length method (VSLM) on laser structures grown on c-plane substrates (sapphire and GaN) with various parameters in the active zone (e.g. QW thickness, numbers of QWs, indium content). After optimization of structural parameters and growth conditions we have been able to achieve positive optical gain above 510 nm with low waveguide losses for our double quantum well (DQW) laser structures. The detailed study of optical gain behaviour reveals a small variation of inhomogeneous broadening of gain spectra with decreasing growth temperature. Additionally, we observe an influence of piezoelectric field on the modal gain amplitude with increasing indium content. Moreover, we discuss the impact of the nonradiative recombination processes on the optical gain. We observe a correlation between defect recombination and the inhomogeneous broadening, associated with the increased strain at high In content.