T. Stacy

Wide band gap electronic materials

Preface. Diamond:- Growth and Doping. Characterization and Properties. Applications. Amorphous and Diamond-Like Carbon Films:- Growth and Doping. Characterization and Properties. Applications. Other Wide Band Gap Semiconductors:- Growth and Doping. Characterization and Properties. Applications. Oral Presentations. Poster Presentations. Author Index. Key Word Index.

Silver on diamond Schottky diodes formed on boron doped hot‐filament chemical vapor deposited polycrystalline diamond films

Schottky diodes were fabricated using sputter deposited silver contacts to boron doped polycrystalline diamond thin films grown by a hot‐filament chemical vapor deposition process with trimethyl borate as an in situ dopant source. High forward current density and a high forward‐to‐reverse current ratio were exhibited by these diodes. Current density‐voltage and capacitance‐voltage‐frequency characteristics of these diodes are very similar to those of Schottky diodes fabricated using a single‐crystal diamond substrate.

Effect of mechanical stress on current-voltage characteristics of thin film polycrystalline diamond Schottky diodes

Schottky diodes utilized for mechanical stress effect studies were fabricated using aluminum contacts to polycrystalline diamond thin films grown by a hot‐filament‐assisted chemical vapor deposition process. Compressive stress was found to have a large effect on the forward biased current‐voltage characteristics of the diode, whereas the effect on the reverse biased characteristics was relatively small. This stress effect on the forward biased diamond Schottky diode was attributed to piezojunction and piezoresistance effects that dominated the diode current‐voltage characteristics in the small and large bias regions, respectively. At a large constant forward bias current, a good linear relationship between output voltage and applied force was observed for force of less than 10 N, as predicted by the piezoresistance effect. The measured force sensitivity of the diode was as high as 0.75 V/N at 1 mA forward bias. Compared to either silicon or germanium junction diodes and tunnel diodes, polycrystalline diam...

Growth of oriented aluminium nitride films on silicon by chemical vapour deposition

Aluminium nitride films were grown on silicon substrates using the chemical vapour deposition (CVD) method. The properties of the films were studied by scanning electron microscopy (SEM), atomic force microscope (AFM) measurements, X-ray diffraction and Raman scattering. The resulting films were strongly textured and had a preferential orientation with the c-axis normal to the surface, the Raman spectra showed two peaks at 607 and 653 cm−1 and two large bands at 750 and 900 cm−1 of smaller intensity. Both the macro- and micro-Raman spectra showed the same peaks.

Plasma etched polycrystalline hot-filament chemical vapor deposited diamond thin films and their electrical characteristics

Etching of hot‐filament, chemical vapor deposited, diamond thin films utilizing low energy ion irradiation was investigated. The films used in this study were boron doped polycrystalline diamond, deposited on p‐type (100) oriented silicon substrates. A low voltage dc corona discharge with an oxygen plasma was used to sputter etch the films. Surfaces were investigated by scanning electron microscopy and profilometry. Etch rates were approximately 500 A/min, depending on the various processing conditions. Characteristics of In/diamond/Si Schottky diodes were used to evaluate the electrical properties of diamond surfaces with various treatments. Results indicate that plasma etching can significantly affect Schottky device characteristics.

Diamond photovoltaic cells as a first-wall material and energy conversion system for inertial confinement fusion

Diamond technology is a major area of worldwide semiconductor research. It has been said that the current status of diamond semiconductor technology is similar to that of silicon technology in 1960. Most of the research on diamond is in high quality film production (e.g., purity, and single crystalline versus polycrystalline). A few groups are concentrating on the development of diamond electronic devices. In this endeavor, both p-type and n-type diamond films have been produced. The p-type diamond has excellent properties while the ntype diamond is very high resistance. A primitive p-n junction has been demonstrated. Several groups have demonstrated Schottky diodes including the high bandgap semiconductor group at the University of Missouri-Columbia.

Considerations in Further Development of Aluminum Nitride as a Material for Device Applications

Development of aluminum nitride as a wide bandgap semiconductor is in its initial stages. An overview of this unique material is presented and some of the major issues in materials deposition, characterization, as well as device applications are discussed. Consideration of defects, dopants, and initial results on development of rectifying junctions are presented as well.

Electrical Characterization of Aluminum Nitride Films on Silicon Grown by Chemical Vapor Deposition

Aluminum nitride (AlN) films were grown on silicon (Si) substrates by chemical vapor deposition (CVD). The films were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD). The refractive index of the AlN films was determined by ellipsometry. Current-voltage and current-temperature characteristics were performed on metal-AlN-p + Si structures with Pt, Au and Al as metal electrodes. The characteristics showed that at high field and high temperature the carrier conduction mechanism in the film was dominated by Frenkel-Poole emission. The relative dielectric constant of the AlN films was estimated to be 9.66+0.3 from capacitance-voltage-frequency (C-V-f) measurements on Au-AlN-p + Si.

HIGH QUANTUM EFFICIENCY FOR PT2SI SCHOTTKY-BARRIER DIODES IN THE VACUUM ULTRAVIOLET

Pt2Si Schottky‐barrier diodes were found to exhibit excellent photoresponse in the wavelength region of 116.4–221.4 nm when they were operated in the front illumination mode. Quantum efficiencies as high as 220% were achieved, depending on the substrate resistivity used and the Pt2Si film thickness.

AIN on diamond thin films grown by chemical vapor deposition methods

Aluminum nitride (AlN) films were grown by chemical vapor deposition (CVD) on boron-doped diamond films deposited by the hot-filament CVD (HFCVD) method. The films were characterized by scanning electron microscopy, x-ray diffraction, and Raman spectroscopy. The electrical characterization of the AlN/diamond interface was performed by current-voltage (I-V) and capacitance- voltage measurements. The resulting films showed one x-ray diffraction peak of (100) oriented AlN and three diamond diffraction peaks of (111), (220) and (331) orientation. The Raman spectra showed two peaks, one at 660 cm-1 due to scattering by the AlN lattice and the other at 1335 cm-1 by the diamond lattice. The I-V measurements on the metal(W)/diamond/Si/Al structure showed ohmic behavior from which the diamond film resistivity of 5 X 105 (Omega) -cm was estimated. The I-V measurements on the W/AlN/diamond/Si/Al structure showed rectifying behavior. The capacitance of the film was independent of the applied voltage and was dominated by the diamond bulk capacitance.