A power semiconductor device includes trenches disposed in a first base layer of a first conductivity type at intervals to partition main and dummy cells, at a position remote from a collector layer of a second conductivity type. In the main cell, a second base layer of the second conductivity type, and an emitter layer of the first conductivity type are disposed. In the dummy cell, a buffer layer of the second conductivity type is disposed. A gate electrode is disposed, through a gate insulating film, in a trench adjacent to the main cell. A buffer resistor having an infinitely large resistance value is inserted between the buffer layer and emitter electrode. The dummy cell is provided with an inhibiting structure to reduce carriers of the second conductivity type to flow to and accumulate in the buffer layer from the collector layer.

Power semiconductor device

An energy harvesting device is provided. The energy harvesting device includes structural members covered with piezoelectric material resonating at different primary frequencies. As the structure to which the energy harvesting device is secured vibrates over a range of frequencies, more than one member resonates or is close to resonance. As such, multiple members work simultaneously to create electrical energy.

Multi-frequency piezoelectric energy harvester

Chemical and electrical properties of the surfaces of GaN and GaN/AlGaN heterostructures were systematically investigated by x-ray photoelectron spectroscopy (XPS), capacitance–voltage, and current–voltage measurements. From in situ XPS study, relatively smaller band bending of 0.6 eV was seen at the GaN (2×2) surface grown by radio frequency-assisted molecular beam epitaxy on the metalorganic vapor phase epitaxy GaN template. After exposing the sample surface to air, strong band bending took place at the surface. The surface treatment in NH4OH solution and N2 plasma was found to reduce the surface Fermi level pinning. Surface passivation process of GaN utilizing SiNx film by electron-cyclotron-resonance assisted plasma chemical vapor deposition (ECR–CVD) achieved low interface state density, 2×1011cm−2 eV−1. No pronounced stress remained at the SiNx/GaN interface, which was confirmed by Raman spectroscopy. The present NH4OH/ECR–N2 plasma treatment was also found to be effective in realizing well-ordered ...

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Chemistry and electrical properties of surfaces of GaN and GaN/AlGaN heterostructures

Electrical characterization of AlN/GaN interfaces was carried out by the capacitance–voltage (C–V) technique in materials grown by metalorganic chemical vapor deposition. The high-frequency C–V characteristics showed clear deep-depletion behavior at room temperature, and the doping density derived from the slope of 1/C2 plots under the deep depletion condition agreed well with the growth design parameters. A low value of interface state density Dit of 1×1011 cm−2 eV−1 or less around the energy position of Ec−0.8 eV was demonstrated, in agreement with an average Dit value estimated from photoassisted C–V characteristics.

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Capacitance–voltage characterization of AlN/GaN metal–insulator–semiconductor structures grown on sapphire substrate by metalorganic chemical vapor deposition

The status of GaAs, SiC and GaN junction field effect transistors (JFETs) is reviewed with a focus on their application to high temperature and high power operation. The advantage of the JFET structure for this operation regime is detailed. Future directions for junction gated transistors are outlined.

A review of junction field effect transistors for high-temperature and high-power electronics

Undoped single crystalline aluminum nitride films were grown on 4H and 6H SiC substrates using metal–organic chemical-vapor deposition at 1200 °C. From in situ reflection high-energy electron diffraction, x-ray diffraction rocking curves, and cathodoluminescence spectra, the crystallinity of the films was confirmed. Atomic force microscopy showed that some films were substantially dominated by island growth, rather than step flow growth. Aluminum was evaporated to form metal–insulator–semiconductor (MIS) capacitors for high-frequency capacitance voltage measurements carried out at room temperature. Low leakage made it possible to measure the structures and characterize accumulation, depletion, deep depletion, and, in some cases, inversion. From independent optical thickness measurements, the relative dielectric constant of aluminum nitride was confirmed at 8.4. The flatband voltage of the AlN MIS capacitors on p-type SiC was close to the theoretical value expected. The films were stressed up to 60 V (3 MV...

Investigation of aluminum nitride grown by metal–organic chemical-vapor deposition on silicon carbide

A lateral field effected transistor of SiC for high switching frequencies comprises a source region layer (5) and a drain region layer (6) laterally spaced and highly doped n-type, an n-type channel layer (4) extending laterally and interconnecting the source region layer and the drain region layer for conducting a current between these layers in the on-state of the transistor, and a gate electrode (9) arranged to control the channel layer to be conducting or blocking through varying the potential applied to the gate electrode. A highly doped p-type base layer (12) is arranged next to the channel layer at least partially overlapping the gate electrode and being at a lateral distance to the drain region layer. The base layer is shorted to the source region layer.

A LATERAL FIELD EFFECT TRANSISTOR OF SiC, A METHOD FOR PRODUCTION THEREOF AND A USE OF SUCH A TRANSISTOR

The invention relates to a method for selective etching of SiC, the etching being carried out by applying a positive potential to a layer (3; 8) of p-type SiC being in contact with an etching solution containing fluorine ions and having an oxidising effect on SiC. The invention also relates to a method for producing a SiC micro structure having free hanging parts (i.e. diaphragm, cantilever or beam) on a SiC-substrate, a method for producing a MEMS device of SiC having a free hanging structure, and a method for producing a piezo-resistive pressure sensor comprising the step of applying a positive potential to a layer (8) of p-type SiC being in contact with an etching solution containing fluorine ions and having an oxidising effect on SiC.

Method of producing a semiconductor device of SiC

Feasibility of lo-hi-lo and delta-doped structures for evaluation of high-field silicon carbide material properties is investigated. Delta-doped structures are grown using the hot-wall CVD technique. Aluminum and nitrogen doping profiles are demonstrated with FWHM below 10 nm. Nitrogen doping transients are found to be slower than those for aluminum. The growth interrupt technique has been developed for achieving narrow nitrogen doping peaks. Lo-hi-lo structures were fabricated using the implantation-and-regrowth technique. Structures with confined avalanche multiplication are demonstrated using the lo-hi-lo and delta doping techniques. The effect of substrate imperfections on early avalanche breakdown is investigated using confined avalanche multiplication devices.

Investigation of Lo-Hi-Lo and Delta-Doped Silicon Carbide Structures

Buried-gate field-effect transistors with blocking voltages up to 600-700 V have been fabricated in 6H polytype silicon carbide using a trench technology. The devices achieve drain currents of up to 60 mA for a channel width of 0.72 mm and have a turn off gate voltage of about 40 V. We report on the device characteristics and analyze the performance under high-voltage device operation.

Christopher Harris

Papers

Investigation of aluminum nitride grown by metal–organic chemical-vapor deposition on silicon carbide

A LATERAL FIELD EFFECT TRANSISTOR OF SiC, A METHOD FOR PRODUCTION THEREOF AND A USE OF SUCH A TRANSISTOR

Method of producing a semiconductor device of SiC

Investigation of Lo-Hi-Lo and Delta-Doped Silicon Carbide Structures

High-voltage operation of field-effect transistors in silicon carbide