A nitride-based semiconductor device includes a substrate, a buffer, a first nitride-based semiconductor layer, a second nitride-based semiconductor layer, a S/D electrode, a second S/D electrode, and a gate electrode. The buffer is disposed over the substrate and includes at least one layer of a nitride-based semiconductor compound doped with an acceptor at a top-most portion of the buffer. The first and second nitride-based semiconductor layers are disposed over the buffer. The first S/D electrode is disposed over the second nitride-based semiconductor layer, in which the first S/D electrode extends downward to a position lower than the first nitride-based semiconductor layer, so as to form at least one first interface with the top-most portion of the buffer, making contact with the at least one layer of the nitride-based semiconductor compound. The second S/D electrode and the gate electrode are disposed over the second nitride-based semiconductor layer.

Some embodiments of the disclosure provide a semiconductor device. The semiconductor device comprises: a substrate; a first nitride semiconductor layer on the substrate; a second nitride semiconductor layer on the first nitride semiconductor layer and having a band gap larger than a band gap of the first nitride semiconductor layer; an intermediate layer disposed on the second nitride semiconductor layer; and a conductive structure disposed on the intermediate layer, wherein a first even interface is formed between the intermediate layer and the second nitride semiconductor layer.

A semiconductor unit includes: a barrier layer including a first compound semiconductor; a channel layer including a second compound semiconductor, and bonded to the barrier layer at a first face; an insulation layer provided on a second face, of the barrier layer, that is on an opposite side of the first face, and having an opening section that exposes the barrier layer; a gate electrode provided to bury the opening section; a source electrode and a drain electrode that are provided on the second face of the barrier layer on both sides of the gate electrode with the gate electrode being interposed; and a material layer including a metal material or a semiconductor material, and provided in contact with the second face of the barrier layer between the gate electrode and the drain electrode.

A self-supporting substrate includes a first nitride layer grown by hydride vapor deposition method or ammonothermal method and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium; and a second nitride layer grown by a sodium flux method on the first nitride layer and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium. The first nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the first nitride layer. The second nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the second nitride layer. The first nitride layer has a thickness larger than a thickness of the second nitride layer.

A method for activating implanted dopants and repairing damage to dopant-implanted GaN to form n-type or p-type GaN. A GaN substrate is implanted with n- or p-type ions and is subjected to a high-temperature anneal to activate the implanted dopants and to produce planar n- or p-type doped areas within the GaN having an activated dopant concentration of about 10.sup.18-10.sup.22 cm.sup.−3. An initial annealing at a temperature at which the GaN is stable at a predetermined process temperature for a predetermined time can be conducted before the high-temperature anneal. A thermally stable cap can be applied to the GaN substrate to suppress nitrogen evolution from the GaN surface during the high-temperature annealing step. The high-temperature annealing can be conducted under N.sub.2 pressure to increase the stability of the GaN. The annealing can be conducted using laser annealing or rapid thermal annealing (RTA).

An ohmic contact to a semiconductor layer including a heterostructure barrier layer and a metal layer adjacent to the heterostructure barrier layer is provided. The heterostructure barrier layer can form a two dimensional free carrier gas for the contact at a heterointerface of the heterostructure barrier layer and the semiconductor layer. The metal layer is configured to form a contact with the two dimensional free carrier gas.

A semiconductor device includes a substrate; a first nitride semiconductor layer above the substrate; a second nitride semiconductor layer on the first nitride semiconductor layer; an ohmic electrode above the substrate; and a contact layer in contact with at least a part of the ohmic electrode, the contact layer containing silicon and chlorine. The second nitride semiconductor layer has a wider band gap than the first nitride semiconductor layer. A two-dimensional electron gas channel is formed in the first nitride semiconductor layer at a heterointerface between the first nitride semiconductor layer and the second nitride semiconductor layer. A silicon concentration has a higher peak value than a chlorine concentration in the contact layer.

A High Mobility Electron Transistor (HEMT) and a capacitor co-formed on an integrated circuit (IC) share at least one structural feature, thereby tightly integrating the two components. In one embodiment, the shared feature may be a 2DEG channel of the HEMT, which also functions in lieu of a base metal layer of a conventional capacitor. In another embodiment, a dialectic layer of the capacitor may be formed in a passivation step of forming the HEMT. In another embodiment, a metal contact of the HEMT (e.g., source, gate, or drain contact) comprises a metal layer or contact of the capacitor. In these embodiments, one or more processing steps required to form a conventional capacitor are obviated by exploiting one or more processing steps already performed in fabrication of the HEMT.

Disclosed is a method for reducing contact resistance, including depositing a GST layer on an InGaAs substrate, generating an InGaAs/GST/Ni stacked structure by depositing a Ni layer on the GST layer, and thermally treating the stacked structure to rearrange components of the GST layer and to generate a Ni—InGaAs alloy.

The present description relates to a gallium nitride transistor which includes at least one source/drain structure having low contact resistance between a 2D electron gas of the gallium nitride transistor and the source/drain structure. The low contact resistance may be a result of at least a portion of the source/drain structure being a single-crystal structure abutting the 2D electron gas. In one embodiment, the single-crystal structure is grown with a portion of a charge inducing layer of the gallium nitride transistor acting as a nucleation site.