Beta Silicon Carbide PN Junction Diodes
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*Materials Science Research Center of Excellence, School of Engineering, Howard University Washington, DC 20059, [email protected], [email protected] "**SurfaceModification and Characterization Research Facility-+, Oak Ridge National Laboratory, Oak Ridge, TN 37381, [email protected].
ABSTRACT Beta silicon carbide (3C-SiC) diodes have been fabricated using ion implantation as the selective doping technique. Previous work on 3C-SiC diodes have exhibited properties such as low reverse breakdown voltages and high ideality factors. Also, 6H and 4H SiC diodes have been reported. This paper studies a different procedure to produce better 3C-SiC diodes for use inthe electronics industry. Current versus voltage, capacitance versus voltage and temperature versus voltage tests were conducted on the devices. Isolation between devices is a prominent concern when building integrated circuits. Proton bombardment is the preferred planar process for forming isolation regions in gallium arsenide (GaAs) due to the lack of a stable native oxide. Hydrogen and boron in GaAs have exhibited good electrical isolation between devices. This paper investigates using proton bombardment to form isolation regions in 3C-SiC. Cubic SiC samples are implanted with a variety of implant doses, ranging from 1 x 1014 to I x 1015 ions / cm 2 , and implant energies ranging from 150 to 300 keV. Hall measurement tests were performed to study the characteristics ofthe implanted material. INTRODUCTION SiC is a wide bandgap semiconductor that has found a variety of applications in the electronics industry. The bandgap of SiC is larger than both Si and GaAs, thus devices made from this material will require a higher temperature to reach the intrinsic region of the material.
As a result, SiC is attractive for high temperature electronics. SiC has a higher thermal conductivity than both Si and GaAs, which allows for good heat dissipation and higher packing
densities. SiC has a higher saturation electron drift velocity than Si and GaAs. Furthermore, due to SiC's high breakdown electric field high power switching devices and high power MOSFET's have been fabricated. 1,2 From a optical standpoint, SiC has been used in making blue LED's and other photonic devices. Several polytypes exist for this material such as 2H, 4H, 6H, and 3C, These polytypes represent the growth structure of the SiC atoms. 3C-SiC has the highest electron mobility of the SiC polytypes. Proton bombardment is performed using ion implantation to create damage layers inside a particular substrate. Inside the damage layers are traps inthe conduction band which capture electrons, hence decreasing the conductivity of the material. Isolation between diodes is essential3 for more complex integrated circuits. Proton isolation has been used in GaAs circuits. EXPERIMENT The 3C-SiC was grown at the Materials Science Research Center of Excellence (MSRCE) at Howard University using a horizontal chemical vapor deposition (CVD) reactor. The sample was 12 microns (jim) thick. A growth rate of 2
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