Structural and electrical properties of H-terminated diamond field-effect transistor

A dielectric barrier separating hydrogen induced p-type channel and Al gate metal contact of diamond FET has been investigated. The separation barrier is necessary to prevent tunneling current between the H-induced channel and the gate contact. In this investigation, CV measurements, fitting of forward IV characteristics, TEM and SIMS profiles have been used to obtain a more detailed picture of this barrier layer. While the composition of this layer is not clear, TEM and SIMS measurements indicate that this layer may be connected to a diamond phase or aluminium oxide. Using material properties of these materials, thickness of the separation layer extracted from the CV measurements was between 5-10 nm and the channel sheet change density was above 1 × 10¹³ cm^{- 2}. This thickness is in good agreement with the TEM observations. Frequency dependent CV measurements showed almost no frequency dependence, and no UV light dependence has been observed. Temperature dependent CV measurements showed a decrease of the dielectric constant at 100 °C. Fitting of the forward tunnelling current indicated a thickness of the barrier layer of about 5 nm with a barrier height of 2.4 eV.