GaN 2D photonic crystals

D.Peyrade1,2, L.Manin1, D.Coquillat2, R.Legros2, J.Lascaray2, N. Grandjean3 and Y. Chen1

1L2M, 196 Av. H. Ravera, 92225 Bagneux, France
2G.E.S.,Universite Montpellier II, pl. E. Bataillon, 34090 Montpellier, France
2C.R.H.E.A., rue B. Gregory, Sophia Antipolis, Valbonne, France

The realization of nanostructures in large band gap semi-conductors is important for various optical applications. Here, we present a study of the fabrication of 2D GaN photonic crystals.

A theoretical calculation using the plane wave method has been done, showing a photonic band gap for a GaN graphite lattice despite a small dielectric constant (e~6). For instance, a relative large periodicity of our structure (250 nm) gives up a gap for a TM mode propagation in the plane normal to the columns centred on 370nm [Figure 1]. The choice of the graphite structure is motivated by an easy experimental realization with respect to the triangular lattice of holes.

The fabrication of this structure has been performed by electron-beam lithography, lift-off and reactive ion etching of GaN in SiCl4 plasma. As shown in Figure 2, the etched pillars present a sufficient large aspect ratio. The improvement of the verticality of sidewalls and optical characterisation of this structure are underway.