Active photonic crystal (PhC) devices such as lasers are very attractive for integrated optical communication applications. For such devices, InP-based materials are hitherto the main choice for the 1.5 micron wavelength range [1-3]. Concerning the fabrication of PhCs, dry etching while having the advantage of being anisotropic inevitably causes damage to the etched material thus affecting its electrical and optical properties. Since carrier lifetime is a very important figure of merit for active devices it is crucial to investigate the impact of the PhC fabrication on the carrier lifetime in InP-based materials.
This work focuses on the etch-induced modification of the carrier lifetime in two-dimensional PhC structures containing a GaInAsP/InP quantum well (QW) situated at 250 nm below the surface. The PhCs consisting of a triangular lattice of air-holes are dry etched for different durations by Ar/Cl2 chemically assisted ion beam etching with Argon ion energy of 400 eV. For a given etch-duration (hole depth) the measured carrier lifetime depends on the PhC lattice parameters and consistently reduces as the fraction of the etched surface area increases. For an etch depth of about 300 nm, which is comparable to the thickness typically used for 2D PhC membranes, appreciable carrier lifetimes ranging from 1.3 ns to 700 ps at room temperature were obtained. Interestingly, as the hole depth increased from 1 to 3.5 microns the determined non-radiative surface recombination velocity increased from about 3x104 to 2x105 cm/s, thus showing direct evidence for accumulated damage. A qualitative model for the accumulated damage based on the evolution of the hole-shape during etching is provided. Possible role of ion-channeling in generating defects is also discussed. The results of this study are directly relevant to deeply etched PhCs in low index contrast systems as well as for those on membranes.
[1] H. G. Park et. al., Science 305, 1444 (2004)
[2] S. de Rossi et. al., J. Lightwave Technol. 23, 1363 (2005)
[3] B. Ben Bakir et. al., Appl. Phys. Lett. 88, Art.no. 081113 (2006)
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