Transparent Nanocrystalline Diamond Contacts for SiC Devices

Solution Overview

Problem

Current conductive thin films are not suitable for ultra-violet range applications, limiting their use in defect analysis and device performance in wide-band gap semiconductors like SiC and GaN, as they are not transparent to UV light and hinder optical beam induced current imaging studies.

Innovation Solution

Nanocrystalline diamond (NCD) thin films with high optical transmission in the UV range are deposited on semiconductor structures, providing a conductive and transparent contact that allows for simultaneous electrical and optical characterization, and can be doped or undoped to suit various applications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional metal contacts are used, then electrical conductivity is achieved, but UV light transmission is blocked

Engineering Contradiction:

Improveelectrical conductivityVSAvoidUV light transmission

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The patent changes the material parameters by using nanocrystalline diamond with specific grain sizes (nanometer scale) and controlled doping levels, which fundamentally alters the optical and electrical properties to achieve both UV transparency and conductivity simultaneously

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material strategy by combining nanocrystalline diamond structure with controlled doping (boron or phosphorus), creating a material that exhibits both optical transparency in UV range and electrical conductivity through the composite structural and compositional design

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If ITO or ZnO transparent films are used, then UV transparency is improved, but adhesion to semiconductor surface deteriorates

Engineering Contradiction:

ImproveUV transparencyVSAvoidadhesion to semiconductor surface

Core Design Contradiction:

Illumination intensityVSStrength

Solution Approach 1:

The patent changes the material parameters by using nanocrystalline diamond with specific grain sizes (nanometer scale) and controlled doping levels, which fundamentally alters the optical and electrical properties to achieve both UV transparency and conductivity simultaneously

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a low-cost chemical vapor deposition process that can be completed in a single step without requiring complex multi-layer structures or additional adhesion layers, making the process simpler and more cost-effective than conventional approaches

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If metal contact grids are used, then conductivity is maintained, but material features are obscured

Engineering Contradiction:

ImproveconductivityVSAvoidmaterial features visibility

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent changes the material parameters by using nanocrystalline diamond with specific grain sizes (nanometer scale) and controlled doping levels, which fundamentally alters the optical and electrical properties to achieve both UV transparency and conductivity simultaneously

Inventive Principle:

Principle #35Parameter changes

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

NCD films offer high adhesion, conductivity, and UV transparency, reducing total internal reflection and enabling efficient defect imaging and improved light extraction in GaN-based devices, while being non-destructive and patternable for various semiconductor applications.

Implementation Method 1

Nanocrystalline diamond (NCD) thin films with high optical transmission in the UV range

Methodology Applied

Scientific EffectOptical transmission: Absorption (EM radiation)

Implementation Method 2

a material that is relatively transparent in the ultraviolet wavelengths that will strongly adhere to the semiconductor surface

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 3

The NCD films were n-type or p-type doped or undoped

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS8445383B2Transparent nanocrystalline diamond contacts to wide bandgap semiconductor devices

Publication Date: 2013.05.21 THE GOVERNMENT OF THE UNITED STATES OF AMERICA AS REPRESENTED BY THE SECRETARY DEPARTMENT OF HEALTH & HUMAN SERVICES

AI summary

A heterojunction between thin films of NCD and 4H—SiC was developed. Undoped and B-doped NCDs were deposited on both n− and p− SiC epilayers. I-V measurements on p+ NCD/n− SiC indicated Schottky rectifying behavior with a turn-on voltage of around 0.2 V. The current increased over eight orders of magnitude with an ideality factor of 1.17 at 30° C. Ideal energy-band diagrams suggested a possible conduction mechanism for electron transport from the SiC conduction band to either the valence band or acceptor level of the NCD film.