Regensburg 2016 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 99: Gallium Nitride: Devices

HL 99.9: Vortrag

Freitag, 11. März 2016, 12:15–12:30, H17

Impact of a GaN:Ge/GaN based distributed Bragg reflector on the optical properties of an InGaN LED structure — •Andreas Voß, Gordon Schmidt, Christoph Berger, Stefan Sterling, Frank Bertram, Armin Dadgar, André Strittmatter, and Jürgen Christen — Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany

The Burstein-Moss effect as present in highly Ge-doped GaN leads to a reduction of the refractive index of GaN:Ge as compared to undoped GaN. The resulting refractive index contrast of 2% is sufficient to realize strain free, highly reflective, and narrow band distributed Bragg reflectors (DBR) by combining highly Ge-doped and undoped GaN quarter-wavelength layers.

We report on the optical properties of an InGaN LED structure grown on top of a modulation-doped DBR by metal-organic vapor phase epitaxy (MOVPE) using an AlGaN/sapphire template. The DBR consists of 100 pairs GaN/GaN:Ge λ/4 layers. An InGaN/GaN multiple quantum well embedded in a pn-junction acts as active region.

Spatially resolved electroluminescence (EL) measurements exhibit a convolution of the MQW luminescence with the DBR reflectivity which leads to a drastically reduced linewidth at 430 nm. Detailed analysis of the local reflectivity on micrometer scale reveals spatial fluctuations of the stopband position.