High-Speed Nonpolar InGaN/GaN Superluminescent Diode With 2.5 GHz Modulation Bandwidth

We demonstrate a superluminescent diode fabricated on a nonpolar {m} -plane GaN substrate by employing a linearly tapered waveguide design. A high electrical −3dB modulation bandwidth ( f_{\mathbf {3dB}} ) of 2.5 GHz at a current density of 30 kA/cm 2 is achieved. The high modulation bandwidth is attributed to the shorter carrier recombination lifetime, the linear gain curve in the nonpolar {m} -plane quantum wells, and the ability to operate at high current densities while effectively suppressing lasing. We derive a general expression for the −3dB bandwidth as a function of current density for SLDs using a similar approach to that for laser diodes. The −3dB bandwidth of a nonpolar superluminescent diode increases exponentially with current density. The experimental results are consistent with the derived expression for f_{\mathbf {3dB}} vs . current density.