Single Crystalline CVD Diamond Based Devices for Power Electronics Applications

Sammanfattning: Chemical vapor deposited single-crystalline diamond has rare material properties such as thermal conductivity five times as high as copper, a wide band gap, a high breakdown field and high carrier mobilities. This makes it a very interesting material for high power, high frequency and high temperature applications. In this thesis work, metal oxide semiconductor (MOS) capacitors of diamond substrate were fabricated and analyzed. The MOS capacitor is a building block of the metal oxide semiconductor field effect transistor (MOSFET). Capacitance-voltage (C-V) measurements can provide useful information of the operation of a MOS. Electrical characterization by C-V and current-voltage (I-V) measurements at temperatures ranging from 20 to 150 degrees Celsius were performed on the MOS capacitors to examine flatband and threshold voltages, oxide charge, and oxide thickness. At elevated temperatures, low frequency C-V curves with threshold voltages of approximately 5 V were obtained for MOS capacitors consisting of aluminum gates, a 30 nm layer of aluminum oxide, and boron doped diamond with acceptor concentration 3.1 x 1017 cm-3. The C-V measurements also showed large variations in flatband voltage for different contacts of the MOS capacitor, indicating the presence of oxide charge. Oxide thickness was also extracted from the C-V measurements, typically showing thicknesses around 15-19 nm. Also in this  thesis, an alternative method for reducing the electric field strength around the edges of the contact of a Schottky diode has been examined. This method consists of alternating the geometry by etching the semiconductor where the contact is to be placed. Simulations performed in Comsol Multiphysics showed that a reduction of the field strength of approximately 30 % at the contacts could be achieved by etching the substrate.