Fabricating gratings on nitrides grown by MOVPE for DFB lasers

In an achievement we believe marks a first, we succeeded in fabricating corrugation gratings in indium-nitride (InN) films grown by metal organic vapor phase epitaxy (MOVPE) for distributed feedback lasers. The resulting temperature-independent devices are suitable for wavelength demultiplexing and modulation in optical communications systems. The grating periods are in the first-order wavelength region of 1.55 μm. We also formed gratings in gallium nitride epitaxial layers, applying electron-beam (EB) lithography to form grating patterns in nitride substrates and inductively-coupled plasma reactive ion etching (ICP-RIE) to transfer EB resist patterns to nitrides. The depth of the grating grooves can be controlled by adjusting ICP-RIE etching times to attain suitable coupling coefficients for forward and backward propagating waves in DFB lasers. We also introduce UV imprinting, a new grating fabrication technique that offers significant promise.