Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 18: Focussed Session: Strong Light Matter Coupling I

HL 18.7: Talk

Tuesday, March 23, 2010, 12:00–12:15, H13

Growth and characterization of II-VI-based Bragg reflectors for the blue-violet spectral region — •Sebastian Klembt, Carsten Kruse, and Detlef Hommel — Institute of Solid State Physics, Semiconductor Epitaxy, University of Bremen, Otto-Hahn-Allee NW1, 28359 Bremen, Germany

The objective is to realize surface emitters for the blue to violet spectral range from 400 to 460 nm using II-VI materials. For this purpose, highly reflective distributed Bragg reflectors (DBRs) are necessary. Since the standard high index material ZnSSe is absorbing at 460 nm, it has to be alloyed to achieve a higher bandgap. The investigated structures consist of ZnMgSSe layers for the high refractive index material and MgS/ZnCdSe superlattices for the low index material. One main challenge is to achieve sharp DBR interfaces when the Mg content of the quaternary ZnMgSSe layers is higher than 20%. Furthermore, the requirement of lattice matching to the GaAs substrate needs precise control of deposition parameters during the DBR growth run. High-resolution X-ray diffraction (HRXRD) measurements were performed for calibration of the composition. In order to determine the exact quarterwave thickness of each layer, the use of in-situ reflectometry turned out to be crucial.

A 16 pairs DBR with a stopband centered at 460 nm reaches a reflectivity exceeding 98%, while the stopband width is about 35 nm. Vertical resonators formed by two DBR mirrors and a cavity containing binary ZnSe quantum wells will also be discussed.