Abstract: High electron mobility transistors (HEMTs) and methods of manufacturing the same. A HEMT may include a channel layer and a channel supply layer, and the channel supply layer may be a multilayer structure. The channel supply layer may include an etch stop layer and an upper layer on the etch stop layer. A recess region may be in the upper layer. The recess region may be a region recessed to an interface between the upper layer and the etch stop layer. A gate electrode may be on the recess region.

Abstract: Example embodiments relate to a method of forming a core-shell structure. According to a method, a region in which the core-shell structure will be formed is defined on a substrate, and a core and a shell layer may be sequentially stacked in the defined region. A first shell layer may further be formed between the substrate and the core. When the core and the shell layer are sequentially stacked in the core-shell region, the method may further include forming a groove on the substrate, forming the first shell layer covering surfaces of the groove, forming the core in the groove of which surfaces are covered by the first shell layer, and forming a second shell layer covering the core.

Abstract: According to example embodiments, a high electron mobility transistor (HEMT) includes a channel layer; a channel supply layer on the channel layer; a source electrode and a drain electrode spaced apart from each other on one of the channel layer and the channel supply layer; a gate electrode on a part of the channel supply layer between the source electrode and the drain electrode; a first depletion-forming layer between the gate electrode and the channel supply layer; and a at least one second depletion-forming layer on the channel supply layer between the gate electrode and the drain electrode. The at least one second depletion-forming layer is electrically connected to the source electrode.

Abstract: A method of packaging power devices at a wafer level is disclosed. The method includes preparing a wafer having a plurality of nitride power devices thereon, each of the plurality of nitride power devices having a plurality of electrodes thereon; forming a polymer layer on the plurality of nitride power devices; exposing each of the electrodes from the polymer layer; forming a solder bump on the exposed electrodes; forming a molding layer covering the solder bump on the polymer layer; and removing the wafer and exposing the solder bump.

Abstract: According to example embodiments, a HEMT includes a channel supply layer on a channel layer, a p-type semiconductor structure on the channel supply layer, a gate electrode on the p-type semiconductor structure, and source and drain electrodes spaced apart from two sides of the gate electrode respectively. The channel supply layer may have a higher energy bandgap than the channel layer. The p-type semiconductor structure may have an energy bandgap that is different than the channel supply layer. The p-type semiconductor structure may include a hole injection layer (HIL) on the channel supply layer and be configured to inject holes into at least one of the channel layer and the channel supply in an on state. The p-type semiconductor structure may include a depletion forming layer on part of the HIL. The depletion forming layer may have a dopant concentration that is different than the dopant concentration of the HIL.

Abstract: A higher electron mobility transistor (HEMT) and a method of manufacturing the same are disclosed. According to example embodiments, the HEMT may include a channel supply layer on a channel layer, a source electrode and a drain electrode that are on at least one of the channel layer and the channel supply layer, a gate electrode between the source electrode and the drain electrode, and a source pad and a drain pad. The source pad and a drain pad electrically contact the source electrode and the drain electrode, respectively. At least a portion of at least one of the source pad and the drain pad extends into a corresponding one of the source electrode and drain electrode that the at least one of the source pad and the drain pad is in electrical contact therewith.

Abstract: A high electron mobility transistor (HEMT) according to example embodiments includes a channel layer, a channel supply layer on the channel layer, a source electrode and a drain electrode on at least one of the channel layer and the channel supply layer, a gate electrode between the source electrode and the drain electrode, and a Schottky electrode forming a Schottky contact with the channel supply layer. An upper surface of the channel supply layer may define a Schottky electrode accommodation unit. At least part of the Schottky electrode may be in the Schottky electrode accommodation unit. The Schottky electrode is electrically connected to the source electrode.

Abstract: According to example embodiments, High electron mobility transistors (HEMTs) may include a discontinuation region in a channel region. The discontinuation region may include a plurality of 2DEG unit regions that are spaced apart from one another. The discontinuation region may be formed at an interface between two semiconductor layers or adjacent to the interface. The discontinuation region may be formed by an uneven structure or a plurality of recess regions or a plurality of ion implantation regions. The plurality of 2DEG unit regions may have a nanoscale structure. The plurality of 2DEG unit regions may be formed in a dot pattern, a stripe pattern, or a staggered pattern.

Abstract: An Enhancement-mode (E-mode) high electron mobility transistor (HEMT) includes a channel layer with a 2-Dimensional Electron Gas (2DEG), a barrier layer inducing the 2DEG in the channel layer, source and drain electrodes on the barrier layer, a depletion layer on the barrier layer between the source and drain electrodes, and a gate electrode on the depletion layer. The barrier layer is recessed below the gate electrode and the depletion layer covers a surface of the recess and extends onto the barrier layer around the recess.

Abstract: According to example embodiments, a high electron mobility transistor (HEMT) includes: stack including a buffer layer, a channel layer containing a two dimensional electron gas (2DEG) channel, and a channel supply layer sequentially stacked on each other, the stack defining a first hole and a second hole that are spaced apart from each other. A first electrode, a second electrode, and third electrode are spaced apart from each other along a first surface of the channel supply layer. A first pad is on the buffer layer and extends through the first hole of the stack to the first electrode. A second pad is on the buffer layer and extends through the second hole of the stack to the second electrode. A third pad is under the stack and electrically connected to the third electrode.

Abstract: Power electronic devices including 2-dimensional electron gas (2DEG) channels and methods of manufacturing the same. A power electronic device includes lower and upper material layers for forming a 2DEG channel, and a gate contacting an upper surface of the upper material layer. A region below the gate of the 2DEG channel is an off region where the density of a 2DEG is reduced or zero. The entire upper material layer may be continuous and may have a uniform thickness. A region of the upper material layer under the gate contains an impurity for reducing or eliminating a lattice constant difference between the lower and upper material layers.

Abstract: Provided is a semiconductor device that may include a switching device having a negative threshold voltage, and a driving unit between a power terminal and a ground terminal and providing a driving voltage for driving the switching device. The switching device may be connected to a virtual ground node having a virtual ground voltage that is greater than a ground voltage supplied from the ground terminal and may be turned on when a difference between the driving voltage and the virtual ground voltage is greater than the negative threshold voltage.

Abstract: A transistor includes a device portion and a collector layer. The device portion is in a first side of a semiconductor substrate, and includes a gate and an emitter. The collector layer is on a second side of the semiconductor substrate, which is opposite to the first side. The collector layer is an impurity-doped epitaxial layer and has a doping profile with a non-normal distribution.

Abstract: According to example embodiments, a high electron mobility transistor (HEMT) includes a channel supply layer and a channel layer. The channel layer may include an effective channel region and a high resistivity region. The effective channel region may be between the high resistivity region and the channel supply layer. The high resistivity region may be a region into which impurities are ion-implanted. According to example embodiments, a method of forming a HEMT includes forming a device unit, including a channel layer and a channel supply layer, on a first substrate; adhering a second substrate to the device unit; removing the first substrate; and forming a high resistivity region by ion-implanting impurities into at least a portion of the channel layer.

Abstract: According to example embodiments, a substrate structure may include a GaN-based third material layer, a GaN-based second material layer, a GaN-based first material layer, and a buffer layer on a non-GaN-based substrate. The GaN-based first material layer may be doped with a first conductive type impurity. The GaN-based second material layer may be doped with a second conductive type impurity at a density that is less than a density of the first conductive type impurity in the first GaN-based material layer. The GaN-based third material layer may be doped with a first conductive type impurity at a density that is less than the density of the first conductive type impurity of the GaN-based first material layer. After a second substrate is attached onto the substrate structure, the non-GaN-based substrate may be removed and a GaN-based vertical type semiconductor device may be fabricated on the second substrate.

Abstract: Provided is a chemical sensor that may include a first electrode on a substrate, a sensing member covering the first electrode on the substrate, and a plurality of second electrodes on a surface of the sensing member exposing the surface of the sensing member. The chemical sensor may be configured to measure the change in electrical characteristics when a compound to be sensed is adsorbed on the sensing member. Provided also is a chemical sensor array including an array of chemical sensors.

Abstract: High electron mobility transistors (HEMTs) including a substrate and a HEMT stack on the substrate, the HEMT stack including a compound semiconductor layer that includes a 2-dimensional electron gas (2DEG), an upper compound semiconductor layer that has a polarization index higher than a polarization index of the compound semiconductor layer, and a source electrode, a drain electrode, and a gate that are disposed on the upper compound semiconductor layer. The substrate may be a nitride substrate that has a dielectric constant and a thermal conductivity higher than a dielectric constant and a thermal conductivity of a silicon substrate. The substrate may include an insulating layer that has a dielectric constant and a thermal conductivity higher than a dielectric constant and a thermal conductivity of the silicon substrate, a metal layer that is deposited on the insulating layer, and a plate that is attached to the metal layer.

Abstract: High electron mobility transistors (HEMTs) including a cavity below a drain and methods of manufacturing HEMTS including removing a portion of a substrate below a drain.

Abstract: High electron mobility transistors (HEMTs) and methods of manufacturing the same. A HEMT may include a channel layer and a channel supply layer, and the channel supply layer may be a multilayer structure. The channel supply layer may include an etch stop layer and an upper layer on the etch stop layer. A recess region may be in the upper layer. The recess region may be a region recessed to an interface between the upper layer and the etch stop layer. A gate electrode may be on the recess region.

Abstract: A phase change memory device includes a switching device and a storage node connected to the switching device. The storage node includes a bottom stack, a phase change layer disposed on the bottom stack and a top stack disposed on the phase change layer. The phase change layer includes a unit for increasing a path of current flowing through the phase change layer and reducing a volume of a phase change memory region. The area of a surface of the unit disposed opposite to the bottom stack is greater than or equal to the area of a surface of the bottom stack in contact with the phase change layer.