GaN Transistor Single-Crystal Source/Drain Structure

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Solution Overview

Problem

Gallium nitride transistors face high contact resistance issues between the source/drain structures and the 2D electron gas, limiting their on-state resistance and efficiency in power management and radio frequency applications.

Innovation Solution

A single-crystal source/drain structure is grown with a portion of the charge inducing layer acting as a nucleation site, reducing contact resistance by epitaxially regrowing indium gallium nitride or gallium nitride to abut the 2D electron gas, using techniques like MOCVD or MBE.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional source/drain structures are used in gallium nitride transistors, then manufacturing is simpler, but contact resistance to 2D electron gas is high (470 ohm-μm)

Engineering Contradiction:

Improvecontact resistanceVSAvoidfabrication complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The charge inducing layer is formed beforehand to serve as a nucleation site for epitaxial regrowth. This preliminary action enables the subsequent formation of single-crystal source/drain structures with low contact resistance, transforming the high contact resistance problem into a solvable fabrication sequence.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the crystal structure parameter from polycrystalline to single-crystal by utilizing epitaxial regrowth on the charge inducing layer. This parameter change in crystal structure directly reduces contact resistance from 470 ohm-μm to 130 ohm-μm or lower.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If single-crystal source/drain structure is grown via epitaxial regrowth, then contact resistance decreases to 130 ohm-μm or lower, but fabrication process becomes more complex

Engineering Contradiction:

Improveon-state resistanceVSAvoidfabrication process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The charge inducing layer acts as an intermediary between the gallium nitride layer and the source/drain structure. It serves as a nucleation site that facilitates epitaxial regrowth, enabling the formation of single-crystal structures without requiring entirely new fabrication processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention replaces conventional mechanical contact formation with epitaxial regrowth processes (MOCVD or MBE). This substitution grows single-crystal structures in-situ, achieving low contact resistance through crystallographic continuity rather than physical contact.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If tighter pitch fabrication is enabled by reduced contact resistance, then device density increases, but manufacturing precision requirements increase

Engineering Contradiction:

Improvedevice densityVSAvoidpitch control

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The charge inducing layer is selectively formed only in specific regions where source/drain structures will be created. This local quality approach enables tighter pitch fabrication by confining epitaxial regrowth to precise locations, improving pitch control while increasing device density.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach significantly lowers contact resistance from 470 ohm-μm to 130 ohm-μm or lower, reducing the on-state resistance of gallium nitride transistors and enabling tighter pitch fabrication and improved electron mobility.

Implementation Method 1

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 2

A single-crystal source/drain structure is grown with a portion of the charge inducing layer acting as a nucleation site

Methodology Applied

Scientific EffectNucleation: Nucleation

Implementation Method 3

using techniques like MOCVD or MBE

Methodology Applied

Scientific EffectChemical Vapour Deposition: Chemical Vapour Deposition

Implementation Method 4

using techniques like MOCVD or MBE

Methodology Applied

Scientific EffectMolecular Beam Epitaxy: Chemical Beam Epitaxy

Data Source

PatentUS10243069B2Gallium nitride transistor having a source/drain structure including a single-crystal portion abutting a 2D electron gas

Publication Date: 2019.03.26 INTEL CORP

AI summary

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.