Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 18: Focussed Session: Strong Light Matter Coupling I

HL 18.2: Invited Talk

Tuesday, March 23, 2010, 10:00–10:30, H13

Strong light-matter coupling in GaN based semiconductors — •Nicolas Grandjean — EPFL, Switzerland

III-V nitride semiconductors are well suited for short-wavelength optoelectronic devices such as blue light emitting diodes and laser diodes. On the other hand, III-V nitrides are quite promising for the physics of cavity-polaritons. Indeed, GaN possesses intrinsic properties like oscillator strength 10x larger than that of GaAs and exciton binding energy as large as 50 meV in ultra-thin quantum wells (QWs). As a consequence, the light matter-interaction is enhanced allowing the strong coupling regime (SCR) to be sustained at room-temperature (RT). Such characteristics have led to the first demonstration of polariton lasing at 300K.

Optical pumping experiments performed on GaN bulk MCs have already shown the potential of III-V nitride semiconductors for polariton condensation. Recent results obtained on QW-MC indicate polariton condensation at 300K with a very low threshold. As expected, the threshold is dependent on both the temperature and the detuning of the cavity mode with respect to the exciton mode.

Another interesting feature is concerned with the polarization behaviour with increasing the pump power above threshold. A depinning of the polarization is observed resulting in a progressive decrease of the polarization degree of the emitted light.

Finally, we will discuss the perspectives of GaN cavity-polaritons for device applications.