Fabrication of first-order gratings for GaAs/AlGaAs LD's by EB lithography

High-precision first-order gratings, 110 nm pitch, for GaAs/AlGaAs LD's were successfully fabricated using EB lithography. The field stitching error of EB lithography caused by height difference between reference marks for calibration and the samples, was reduced to 5 nm by controlling the EB deflection voltage calibrated by the detection of the position of the marks on the samples. We also investigated the effect of field stitching error on lasing characteristics using measurement and calculation. We found that a 20 nm stitching error is sufficiently small for single-mode LD operation.