Simulation of current spreading in bottom-emitting vertical cavity surface emitting laser for high power operation
School of Engineering and Mathematics
In this paper, a numerical study was conducted on spreading of the current in a bottom emitting Vertical Cavity Surface Emitting Laser (VCSEL) with oxidation at the substrate. It was found that the current density profiles of etched VCSELs with small active diameters (< 125 μm) are similar to unetched VCSELs with a 500 μm active diameter. Larger active diameters of 150 μm to 225 μm also have higher density profiles than unetched VCSELs. The simulated current density profiles of large p-contact diameters are dependent on the oxide aperture diameter rather than the contact diameter. For smaller p-doped contact diameters, the density profiles are dependent on the contact diameter rather than the oxide aperture diameter. From current density profiles, higher output powers in the 980 nm wavelength regime are theoretically obtainable at lower threshold currents than previously reported. Maximum output powers of 489 mW, 690 mA and 787 mA at current thresholds of 102 mA, 271 mA and 442 mA were calculated for contact diameters of 50 μm, 100 μm and 150 μm, respectively, with a 50 μm oxide aperture. Depending on the geometric ratios of the simulated devices, required high output power VCSELs can be designed for specific applications.