Multi-Heterojunction HEMT Structure for Stable Transconductance

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Solution Overview

Problem

The linear operating characteristics of HEMT devices are compromised due to increased series resistance and decreased electron saturation speed, leading to non-linear transconductance with gate-source bias voltage, which affects the performance of high-frequency and high-power semiconductor devices.

Innovation Solution

A semiconductor structure with sequentially stacked heterojunction structures, where the component proportions, thicknesses, and widths of barrier layers are varied to achieve mutual compensation of transconductances, enhancing gate control and maintaining stable transconductance across a wide gate-source bias voltage range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the total barrier layer thickness of the dual channel heterojunction material is increased, then the total concentration of 2DEG increases and device saturation current increases, but the distance between the device gate and the underlying channel increases, which reduces gate control ability and peak transconductance

Engineering Contradiction:

Improvetotal concentration of 2DEGVSAvoiddistance between gate and channel

Core Design Contradiction:

Quantity of substanceVSLength of moving object

Solution Approach 1:

The barrier layer is divided into multiple segments (first barrier layer, second barrier layer, third barrier layer) with different component proportions. This segmentation allows the total barrier thickness to be maintained for high 2DEG concentration while distributing the thickness across multiple layers with varying Al compositions, enabling optimized gate control at different depths

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the barrier structure have different local compositions - the first barrier layer has higher Al proportion for strong field effect near the gate, while lower barrier layers have reduced Al proportion to maintain 2DEG concentration. This local quality variation resolves the contradiction between gate control and carrier concentration

Inventive Principle:

Principle #3Local quality

2Productivity

If the transconductance of HEMT device increases with gate-source bias voltage, then the device can handle higher currents, but the transconductance decreases after reaching peak value, which affects the linearity of the device

Engineering Contradiction:

Improvedevice saturation currentVSAvoidlinearity of transconductance

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The multi-layer barrier structure with varying Al compositions creates dynamically responsive 2DEG distributions that adapt to gate-source bias voltage changes. Each barrier layer contributes differently to transconductance at different voltage levels, enabling the device to maintain stable transconductance across a wide voltage range rather than showing peak-and-decline behavior

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The barrier structure uses composite material design with multiple AlGaN layers having different Al proportions (e.g., 0.25, 0.20, 0.15). This composite structure enables simultaneous optimization of high-current capability through total 2DEG concentration and linearity through distributed transconductance contributions from each layer

Inventive Principle:

Principle #40Composite materials

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 improves the linearity and frequency characteristics of HEMT devices by stabilizing transconductance, increasing saturation current, and maintaining high breakdown voltage and output current, while reducing sheet and contact resistance.

Implementation Method 1

the first heterojunction structure includes a first channel layer and a first barrier layer, the second heterojunction structure includes a second channel layer and a second barrier layer

Methodology Applied

Scientific EffectHeterojunction:

Implementation Method 2

the double channel heterojunction structure can have a higher total concentration of 2DEG, which substantially increases the device saturation current

Methodology Applied

Scientific Effect2DEG formation:

Implementation Method 3

materials of the first barrier layer, the second barrier layer, . . . , and the n-th barrier layer include AlGaN

Methodology Applied

Scientific EffectAlGaN heterostructure:

Implementation Method 4

proportions of Al in the first barrier layer, the second barrier layer, . . . , and the n-th barrier layer gradually decrease layer by layer from bottom to top

Methodology Applied

Scientific EffectCompositional gradient:

Data Source

PatentUS20240063302A1Semiconductor structures

Publication Date: 2024.02.22 ENKRIS SEMICON

AI summary

A semiconductor structure is provided, and comprises: a substrate, an insulation layer and a protruding structure. The insulation layer is located on the substrate, and the protruding structure protrudes from the insulation layer, where the protruding structure further includes a first heterojunction structure, a second heterojunction structure, . . . , and an n-th heterojunction structure that are sequentially stacked in a direction away from the substrate, and n is greater than or equal to 2, wherein the first heterojunction structure includes a first channel layer and a first barrier layer, the second heterojunction structure includes a second channel layer and a second barrier layer, . . . , and the n-th heterojunction structure includes an n-th channel layer and an n-th barrier layer, and component proportions of at least two of the first barrier layer, the second barrier layer, . . . , or the n-th barrier layer are different.