Graded InAlGaN Cap Layer for Semiconductor Contact Resistance

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Solution Overview

Problem

Conventional semiconductor devices with InAlGaN cap layers achieve reduced potential barriers between the cap and electron-supplying layers but result in increased barriers between the ohmic electrode and the cap layer, limiting the reduction of contact resistance.

Innovation Solution

A semiconductor device with a cap layer composition of (InyAl1-y)zGa1-zN that monotonically decreases in z towards the ohmic electrode, maintaining lattice match with the channel layer, to reduce the potential barrier between the ohmic electrode and the cap layer, thereby reducing contact resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the InAlN ratio in the cap layer is increased to reduce the potential barrier with the electron-supplying layer, then the polarization charge increases and potential barrier decreases, but the lattice match with the channel layer becomes more difficult to maintain

Engineering Contradiction:

Improvepotential barrier reduction between cap layer and electron-supplying layerVSAvoidlattice match between cap layer and channel layer

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The cap layer is designed with spatially varying composition: the region near the channel layer maintains composition optimized for lattice matching (lower InAlN ratio), while the region near the electron-supplying layer has higher InAlN ratio optimized for reducing potential barrier. This local quality variation allows simultaneous satisfaction of lattice match requirements and electrical contact requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The cap layer functions as a composite structure with graded composition, combining regions of different InAlN ratios to achieve multiple functions: lattice matching with the channel layer, reduced potential barrier with the electron-supplying layer, and optimized contact with the ohmic electrode. This composite approach resolves the contradiction between lattice match precision and electrical performance.

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

The solution effectively lowers contact resistance by reducing the potential barrier between the ohmic electrode and the cap layer, allowing for a semiconductor device with sufficiently reduced contact resistance.

Implementation Method 1

a cap layer, provided on the electron-supplying layer and creating lattice match with the channel layer

Methodology Applied

Scientific EffectLattice match:

Implementation Method 2

z for the cap layer monotonically decreases as being farther away from the electron-supplying layer... potential barrier between the ohmic electrode and the cap layer can be reduced

Methodology Applied

Scientific EffectPotential barrier reduction:

Data Source

PatentUS8525229B2Semiconductor device

Publication Date: 2013.09.03 RENESAS ELECTRONICS CORP

AI summary

A semiconductor device includes a channel layer, an electron-supplying layer provided on the channel layer, a cap layer provided on the electron-supplying layer and creating lattice match with the channel layer, and ohmic electrodes provided on the cap layer. The cap layer has a composition of (InyAl1-y)zGa1-zN (0≦y≦1, 0≦z≦1). The z for such cap layer monotonically decreases as being farther away from the electron-supplying layer.