AVS 56th International Symposium & Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThA

Invited Paper EM-ThA3
MBE Growth and Optical Properties of GaN Quantum Structures

Thursday, November 12, 2009, 2:40 pm, Room B1

Session: Quantum Structures and Nitrides Devices
Presenter: N. Grandjean, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
Correspondent: Click to Email
In this presentation, we will first address the fabrication of III-V nitride based quantum dots (QDs) using molecular beam epitaxy with ammonia as nitrogen source. We will focus on strain-induced Stranski-Krastanov (SK) growth mode in GaN/AlN system and point out the effect of surface free-energy. It is indeed observed that the V/III ratio controls the 3D island formation in a reversible way. In a second part, we will discuss the optical properties of an ensemble of GaN/AlN QDs. Photoluminescence experiments evidence that the transition energies are dominated by a giant quantum confined Stark effect, which results from the presence of a huge built-in electric field of several MV/cm. This electric field is inherent to wurtzite III-nitride based heterostructures when they are grown along a polar axis. It comes from spontaneous and piezoelectric polarization discontinuities arising at interfaces between different materials. Then, mesa are prepared aimed at single dot spectroscopy using micro-photoluminescence. Optical signatures of excitons and bi-excitons are clearly seen on the luminescence spectra. Both positive and negative binding energies are deduced depending on the dot size. A phenomenological model including the built-in electric field present in the dots well accounts for the experimental observations.