Optimization of low threshold currents in proton implanted vertical cavity surface emitting lasers

This paper presents a simulation analysis for the threshold characteristics of proton implanted vertical-cavity surface-emitting lasers(VCSELs) with the aid of optical-electrical-thermal-gain model. The equations for potential, the carrier density, optical transverse mode and thermal field are given. The distributions of injected current, the fundamental transverse mode, carrier and temperature for VCSELs at various aperture radii of 1,2,4 and 6 microns are studied self-consistently. The threshold injected currents versus the current aperture radii are obtained. The calculated results show that decreasing aperture sizes is an effective method to drop the threshold currents only when the current radii are larger than 2 micron. On the other hand, the threshold currents with the decrease of aperture radii for too small sizes of current aperture. The current aperture radius for low threshold proton implanted VCSEL is found. The threshold currents may drop with improving the confinement of current, while too much small current apertures also damage the threshold. The reason that few VCSEL with smaller aperture radii realize to operate is explained.