S.A. Grot

The effect of surface treatment on the electrical properties of metal contacts to boron-doped homoepitaxial diamond film

Both doped and undoped homoepitaxial diamond films were fabricated using microwave plasma-enhanced chemical vapor deposition (CVD). The conductivity of the diamond film is strongly affected by the surface treatment. In particular, exposure of film surface to a hydrogen plasma results in the formation of a conductive layer which can be used to obtain linear (ohmic) I-V characteristics of the Au/diamond contacts, regardless of the doping level. It is shown how the proper chemical cleaning of the boron-doped homoepitaxial diamond surface allows the fabrication of Au-gate Schottky diodes with excellent rectifying characteristics at temperatures of at least 400 degrees C.<<ETX>>

Electrical characteristics of Schottky diodes fabricated using plasma assisted chemical vapor deposited diamond films

Schottky diodes were fabricated using gold and aluminum contacts to thin diamond films obtained by a microwave plasma assisted chemical vapor deposition process. The current‐voltage and capacitance‐voltage‐frequency characteristics of these devices are similar to those fabricated on a crystalline diamond base formed by traditional ultrahigh pressure process.

High-temperature thin-film diamond field-effect transistor fabricated using a selective growth method

Selective growth of boron-doped homoepitaxial diamond films was achieved using sputtered SiO/sub 2/ as a masking layer. The hole mobility of selectively grown films varied between 210 and 290 cm/sup 2//V-s for hole concentration between 1.0*10/sup 14/ and 6.9*10/sup 14/ cm/sup -3/. The technique was used to fabricate a thin-film diamond field-effect transistor operational at 300 degrees C. The channel resistance of the device is an exponential function of temperature. In combination with the selective growth method, this device can be used as a starting point for the development of high-temperature diamond-based integrated circuits.<<ETX>>

The barrier height of Schottky diodes with a chemical-vapor-deposited diamond base

A barrier height of 1.13±0.03 eV was measured for Al and Au rectifying contacts to p‐type chemical‐vapor‐deposited diamond thin films using the internal photoemission technique. The results are compared with experimental data reported for Schottky barriers on single‐crystal diamond.

High-temperature Schottky diodes with thin-film diamond base

High-temperature (500-580 degrees C) current-voltage (I-V) characteristics of gold contacts to boron-doped homoepitaxial diamond films prepared using a plasma-enhanced chemical vapor deposition (CVD) method are described. Schottky diodes were formed using gold contacts to chemically cleaned boron-doped homoepitaxial diamond films. These devices incorporate ohmic contacts formed by annealing Au(70 nm)/Ti(10 nm) layers in air at 580 degrees C. The experiments with homoepitaxial diamond films show that the leakage current density increases with the contact area. This implies that a nonuniform current distribution exists across the diode, presumably due to crystallographic defects in the diamond film. As a result, Au contacts with an area >1 mm/sup 2/ are essentially ohmic and can be used to form back contacts to Schottky diodes. Schottky diodes fabricated in this matter also show rectifying I-V characteristics in the 25-580 degrees C temperature range.<<ETX>>

Electrical properties of selectively grown homoepitaxial diamond films

Boron‐doped homoepitaxial diamond films were selectively grown using sputtered SiO2 as a masking material. Uniform thickness, down to 50 nm, over a large area can be achieved with this technique. Hall mobility of selectively grown films is comparable to that of high‐pressure high‐temperature synthetic bulk diamond with a corresponding carrier concentration.

Diamond thin-film recessed gate field-effect transistors fabricated by electron cyclotron resonance plasma etching

A new technique for etching boron-doped homoepitaxial diamond films was used to fabricate mesa-isolated recessed gate field-effect transistors that operate at temperatures up to 350 degrees C. The upper temperature range is limited by the gate leakage current. The room-temperature hole concentration and mobility of the diamond film active layer were 1.2*10/sup 13/ cm/sup -3/ and 280 cm/sup 2//V-s, respectively. The maximum transconductance was 87 mu S/mm at 200 degrees C.<<ETX>>

High temperature Schottky diodes with boron-doped homoepitaxial diamond base

Abstract We report the first high temperature operation of thin film diamond based semiconductor devices. Boron-doped homoepitaxial diamond films were grown by microwave plasma assisted chemical vapor deposition using insulating natural diamond substrates. The diamond nature of the films was confirmed by several analytical techniques. Excellent rectifying characteristics were obtained for Au-gate Schottky diodes with homoepitaxial diamond base in the 26–583°C temperature range. Surface cleaning of the films was found to be a key step of the fabrication process.

Rectification and internal photoemission in metal/CVD diamond and metal/CVD diamond/silicon structures

Schottky diodes were formed with free-standing polycrystalline thin film diamond base as well as with polycrystalline diamond films grown on crystalline silicon. Current-voltage and internal photoemission measurements were used to characterize the Schottky diodes and the diamond film. Internal photoemission measurements yielded a barrier height of 1.15 eV. A comparison of experimental data for metal contacts to free-standing diamond films and those on silicon substrates indicates that both rectification and internal photoemission originate at the metal/diamond interface.

Oxygen based electron cyclotron resonance etching of semiconducting homoepitaxial diamond films

Oxygen‐based electron cyclotron resonance (ECR) plasma etching of boron doped homoepitaxial diamond films with no de bias has been achieved. The process was developed to the point where it can provide a uniform and reproducible etching procedure that yields smooth damage‐free etched surfaces. Etch rates attained under these conditions of smooth damage‐free etched surfaced were about 86 A/min.