laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Séminaire - 27 avril 2009

Bruno GAYRAL<br class='autobr' />CEA-CNRS group "Nanophysics and semiconductors"<br class='autobr' />CEA-Grenoble, INAC/SP2M
Optical properties of III-N nanowires grown by MBE

Among the III-V semiconductor family, III-nitrides have quite a few peculiarities. They usually grow in the wurtzite phase, they have quite large piezo-electric constants, the carriers have large effective masses (in GaN and AlN), the band gaps in the III-N family spans from the near IR to the ultra-violet...

Although III-N structures are usually grown with a very large density of structural defects, mass-market applications such as LEDs or blu-ray lasers based on the InGaN/GaN system have been a commercial success for many years. But despite the huge R&D effort made by both industrial and academic laboratories on this system, there is still much to explore and understand on the basic physics of III-N heterostructures.

In this seminar, I will discuss opto-electronics properties of III-N nanowires grown by plasma-assisted MBE on silicon. These structures grow spontaneously anisotropically under certain growth conditions, leading to dense arrays of nanowires with typical diameters in the 30 nm range.

Several features make these structures particularly appealing for fundamental studies and applications. In particular, the large surface to volume ratio allows surface strain relaxation to occur, which considerably reduces the density of structural defects in lattice-mismatched heterostructures in nanowires compared to the 2D structures.

I will present recent results obtained in Grenoble on the photoluminescence study of GaN/AlN insertions embedded in nanowires. In particular, we observe evidence of quantum confined Stark effect in these structures. We also observe a QD-like behavior for such insertions, with in particular the observation of single exciton and biexciton recombination when probing a single insertion in a single nanowire.

I will finally discuss the application potential of such structures for light emitting devices, given the current knowledge on III-N nanowire