The highly conductive surface layer induced in diamond by hydrogen termination has been used to fabricate in-plane gate transistors. The conductive channel has been separated from the Ohmic gate contacts by insulating thin lines, obtained by using a combination of electron-beam lithography with surface oxidation. Oxidized lines of about 100 nm show excellent blocking properties, with leakage current of 0.3 pA/μm at 100 V and room temperature. In-plane transistor properties are reported for operation at 77 K and room temperature with good saturation characteristic and complete pinch-off.

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Device and tuning characteristics of superstructure grating tunable twin-guide (SSG-TTG) laser diodes are presented. The devices are based on the distributed feedback (DFB) TTG laser, but comprise sampled or superstructure gratings in order to utilise Vernier effect tuning to extend the tuning range to potentially several tens of nanometres. In contrast to most other existing monolithic widely tunable semiconductor lasers, this device requires only two tuning currents. The first tuning characteristics show distinct regions of high SMSR where continuous wavelength tuning can be carried out. These regions of high SMSR are spaced in agreement with theoretical predictions that are based on the superstructure grating design. Hence, our observations clearly demonstrate Vernier effect tuning for the first time in a TTG-type laser diode.