Abstract: A DC-coupled two-stage gate driver circuit for driving a junction field effect transistor (JFET) is provided. The JFET can be a wide bandgap junction field effect transistor (JFET) such as a SiC JFET. The driver includes a first turn-on circuit, a second turn-on circuit and a pull-down circuit. The driver is configured to accept an input pulse-width modulation (PWM) control signal and generate an output driver signal for driving the gate of the JFET.

Abstract: Gate drivers for wide bandgap (e.g., >2 eV) semiconductor junction field effect transistors (JFETs) capable of operating in high ambient temperature environments are described. The wide bandgap (WBG) semiconductor devices include silicon carbide (SiC) and gallium nitride (GaN) devices. The driver can be a non-inverting gate driver which has an input, an output, a first reference line for receiving a first supply voltage, a second reference line for receiving a second supply voltage, a ground terminal, and six Junction Field-Effect Transistors (JFETs) wherein the first JFET and the second JFET form a first inverting buffer, the third JFET and the fourth JFET form a second inverting buffer, and the fifth JFET and the sixth JFET form a totem pole which can be used to drive a high temperature power SiC JFET. An inverting gate driver is also described.

Abstract: Wide bandgap semiconductor devices including normally-off VJFET integrated power switches are described. The power switches can be implemented monolithically or hybridly, and may be integrated with a control circuit built in a single- or multi-chip wide bandgap power semiconductor module. The devices can be used in high-power, temperature-tolerant and radiation-resistant electronics components. Methods of making the devices are also described.

Abstract: A method of making a semi-insulating epitaxial layer includes implanting a substrate or a first epitaxial layer formed on the substrate with boron ions to form a boron implanted region on a surface of the substrate or on a surface of the first epitaxial layer, and growing a second epitaxial layer on the boron implanted region of the substrate or on the boron implanted region of the first epitaxial layer to form a semi-insulating epitaxial layer.

Abstract: Semiconductor devices and methods of making the devices are described. The devices can be junction field-effect transistors (JFETs). The devices have raised regions with sloped sidewalls which taper inward. The sidewalls can form an angle of 5° or more from vertical to the substrate surface. The devices can have dual-sloped sidewalls in which a lower portion of the sidewalls forms an angle of 5° or more from vertical and an upper portion of the sidewalls forms an angle of <5° from vertical. The devices can be made using normal (i.e., 0°) or near normal incident ion implantation. The devices have relatively uniform sidewall doping and can be made without angled implantation.

Abstract: A method for rendering a half-bridge circuit containing normally on switches such as junction field effect transistors (JFETS) inherently safe from uncontrolled current flow is described. The switches can be made from silicon carbide or from silicon. The methods described herein allow for the use of better performing normally on switches in place of normally off switches in integrated power modules thereby improving the efficiency, size, weight, and cost of the integrated power modules. As described herein, a power supply can be added to the gate driver circuitry. The power supply can be self starting and self oscillating while being capable of deriving all of its source energy from the terminals supplying electrical potential to the normally on switch through the gate driver. The terminal characteristics of the normally on switch can then be coordinated to the input-to-output characteristics of the power supply.

Abstract: Semiconductor devices and methods of making the devices are described. The devices can be implemented in SiC and can include epitaxially grown n-type drift and p-type trenched gate regions, and an n-type epitaxially regrown channel region on top of the trenched p-gate regions. A source region can be epitaxially regrown on top of the channel region or selectively implanted into the channel region. Ohmic contacts to the source, gate and drain regions can then be formed. The devices can include edge termination structures such as guard rings, junction termination extensions (JTE), or other suitable p-n blocking structures. The devices can be fabricated with different threshold voltages, and can be implemented for both depletion and enhanced modes of operation for the same channel doping. The devices can be used as discrete power transistors and in digital, analog, and monolithic microwave integrated circuits.

Abstract: Semiconductor devices are described wherein current flow in the device is confined between the rectifying junctions (e.g., p-n junctions or metal-semiconductor junctions). The device provides non-punch-through behavior and enhanced current conduction capability. The devices can be power semiconductor devices as such as Junction Field-Effect Transistors (VJFETs), Static Induction Transistors (SITs), Junction Field Effect Thyristors, or JFET current limiters. The devices can be made in wide bandgap semiconductors such as silicon carbide (SiC). According to some embodiments, the device can be a normally-off SiC vertical junction field effect transistor. Methods of making the devices and circuits comprising the devices are also described.

Abstract: Semiconductor devices are described wherein current flow in the device is confined between the rectifying junctions (e.g., p-n junctions or metal-semiconductor junctions). The device provides non-punch-through behavior and enhanced current conduction capability. The devices can be power semiconductor devices as such as Junction Field-Effect Transistors (VJFETs), Static Induction Transistors (SITs), Junction Field Effect Thyristors, or JFET current limiters. The devices can be made in wide bandgap semiconductors such as silicon carbide (SiC). According to some embodiments, the device can be a normally-off SiC vertical junction field effect transistor. Methods of making the devices and circuits comprising the devices are also described.

Abstract: A method for rendering a half-bridge circuit containing normally on switches such as junction field effect transistors (JFETs) inherently safe from uncontrolled current flow is described. The switches can be made from silicon carbide or from silicon. The methods described herein allow for the use of better performing normally on switches in place of normally off switches in integrated power modules thereby improving the efficiency, size, weight, and cost of the integrated power modules. As described herein, a power supply can be added to the gate driver circuitry. The power supply can be self starting and self oscillating while being capable of deriving all of its source energy from the terminals supplying electrical potential to the normally on switch through the gate driver. The terminal characteristics of the normally on switch can then be coordinated to the input-to-output characteristics of the power supply.

Abstract: A method of epitaxially growing a SiC layer on a single crystal SiC substrate is described. The method includes heating a single-crystal SiC substrate to a first temperature of at least 1400° C. in a chamber, introducing a carrier gas, a silicon containing gas and carbon containing gas into the chamber; and epitaxially growing a layer of SiC on a surface of the SiC substrate. The SiC substrate is heated to the first temperature at a rate of at least 30° C./minute. The surface of the SiC substrate is inclined at an angle of from 1° to 3° with respect to a basal plane of the substrate material.

Abstract: Methods of making a semiconductor device such as a lateral junction field effect transistor (JFET) are described. The methods are self-aligned and involve selective epitaxial growth using a regrowth mask material to form the gate or the source/drain regions of the device. The methods can eliminate the need for ion implantation. The device can be made from a wide band-gap semiconductor material such as SiC. The regrowth mask material can be TaC. The devices can be used in harsh environments including applications involving exposure to radiation and/or high temperatures.

Abstract: Wide bandgap semiconductor devices including normally-off VJFET integrated power switches are described. The power switches can be implemented monolithically or hybridly, and may be integrated with a control circuit built in a single-or multi-chip wide bandgap power semiconductor module. The devices can be used in high-power, temperature-tolerant and radiation-resistant electronics components. Methods of making the devices are also described.

Abstract: A self-aligned silicon carbide power MESFET with improved current stability and a method of making the device are described. The device, which includes raised source and drain regions separated by a gate recess, has improved current stability as a result of reduced surface trapping effects even at low gate biases. The device can be made using a self-aligned process in which a substrate comprising an n+-doped SiC layer on an n-doped SiC channel layer is etched to define raised source and drain regions (e.g., raised fingers) using a metal etch mask. The metal etch mask is then annealed to form source and drain ohmic contacts. A single- or multilayer dielectric film is then grown or deposited and anisotropically etched. A Schottky contact layer and a final metal layer are subsequently deposited using evaporation or another anisotropic deposition technique followed by an optional isotropic etch of dielectric layer or layers.

Abstract: A self-aligned silicon carbide power MESFET with improved current stability and a method of making the device are described. The device, which includes raised source and drain regions separated by a gate recess, has improved current stability as a result of reduced surface trapping effects even at low gate biases. The device can be made using a self-aligned process in which a substrate comprising an n+-doped SiC layer on an n-doped SiC channel layer is etched to define raised source and drain regions (e.g., raised fingers) using a metal etch mask. The metal etch mask is then annealed to form source and drain ohmic contacts. A single- or multilayer dielectric film is then grown or deposited and anisotropically etched. A Schottky contact layer and a final metal layer are subsequently deposited using evaporation or another anisotropic deposition technique followed by an optional isotropic etch of dielectric layer or layers.

Abstract: A junction barrier Schottky (JBS) rectifier device and a method of making the device are described. The device comprises an epitaxially grown first n-type drift layer and p-type regions forming p+-n junctions and self-planarizing epitaxially over-grown second n-type drift regions between and, optionally, on top of the p-type regions. The device may include an edge termination structure such as an exposed or buried P+ guard ring, a regrown or implanted junction termination extension (JTE) region, or a “deep” mesa etched down to the substrate. The Schottky contact to the second n-type drift region and the ohmic contact to the p-type region together serve as an anode. The cathode can be formed by ohmic contact to the n-type region on the backside of the wafer. The devices can be used in monolithic digital, analog, and microwave integrated circuits.

Abstract: A switching element combining a self-aligned, vertical junction field effect transistor with etched-implanted gate and an integrated antiparallel Schottky barrier diode is described. The anode of the diode is connected to the source of the transistor at the device level in order to reduce losses due to stray inductances. The SiC surface in the SBD anode region is conditioned through dry etching to achieve a low Schottky barrier height so as to reduce power losses associated with the turn on voltage of the SBD.

Abstract: Semiconductor devices and methods of making the devices are described. The devices can be implemented in SiC and can include epitaxially grown n-type drift and p-type trenched gate regions, and an n-type epitaxially regrown channel region on top of the trenched p-gate regions. A source region can be epitaxially regrown on top of the channel region or selectively implanted into the channel region. Ohmic contacts to the source, gate and drain regions can then be formed. The devices can include edge termination structures such as guard rings, junction termination extensions (JTE), or other suitable p-n blocking structures. The devices can be fabricated with different threshold voltages, and can be implemented for both depletion and enhanced modes of operation for the same channel doping. The devices can be used as discrete power transistors and in digital, analog, and monolithic microwave integrated circuits.

Abstract: A vertical junction field effect transistor (VJFET) having a mesa termination and a method of making the device are described. The device includes: an n-type mesa on an n-type substrate; a plurality of raised n-type regions on the mesa comprising an upper n-type layer on a lower n-type layer; p-type regions between and adjacent the raised n-type regions and along a lower sidewall portion of the raised regions; dielectric material on the sidewalls of the raised regions, on the p-type regions and on the sidewalls of the mesa; and electrical contacts to the substrate (drain), p-type regions (gate) and the upper n-type layer (source). The device can be made in a wide-bandgap semiconductor material such as SiC. The method includes selectively etching through an n-type layer using a mask to form the raised regions and implanting p-type dopants into exposed surfaces of an underlying n-type layer using the mask.

Abstract: Junction field-effect transistors with vertical channels and self-aligned regrown gates and methods of making these devices are described. The methods use techniques to selectively grow and/or selectively remove semiconductor material to form a p-n junction gate along the sides of the channel and on the bottom of trenches separating source fingers. Methods of making bipolar junction transistors with self-aligned regrown base contact regions and methods of making these devices are also described. The semiconductor devices can be made in silicon carbide.