III-V Nitride Thermoelectric Device Using Stacking Faults
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Solution Overview
Problem
The high thermal conductivity of III-V nitride semiconductors limits their application in thermoelectric devices, despite their high electrical conductivity and unipolar nature at high temperatures, resulting in a low figure of merit (ZT) due to excessive heat dissipation.
Innovation Solution
Introducing randomly located dislocations and high-density stacking faults, or microscopic alloy fluctuations in In-containing layers, which disrupt phonon propagation and enhance the Seebeck coefficient through thermionic emission, while maintaining high electrical conductivity, using nonpolar/semipolar GaN technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If III-V nitride semiconductor is used for thermoelectric device, then electrical conductivity is high and unipolar nature is maintained at high temperatures, but thermal conductivity is too large causing excessive heat dissipation
Solution Approach 1:
The patent changes the physical parameters of the nitride semiconductor by introducing dislocations and stacking faults, which alter the phonon transport properties while maintaining electrical conductivity. This reduces thermal conductivity without sacrificing the unipolar nature at high temperatures
Solution Approach 2:
The patent creates a composite structure within the nitride semiconductor by introducing dislocation networks and stacking fault regions that act as phonon scattering centers, effectively creating a composite material with tailored thermal and electrical transport properties
2Loss of energy
If dislocations and stacking faults are introduced to reduce thermal conductivity, then phonon propagation is disrupted and Seebeck coefficient is enhanced, but structural perfection is compromised
Solution Approach 1:
The patent converts the harmful effect of dislocations and stacking faults (which normally degrade material quality) into a beneficial effect by using them as phonon scattering centers to reduce thermal conductivity and enhance thermoelectric performance
Solution Approach 2:
The patent introduces dislocations and stacking faults locally within specific regions of the nitride semiconductor to create phonon scattering centers, while maintaining overall structural integrity and electrical transport properties in other regions
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 effectively reduces thermal conductivity while preserving electrical conductivity, enhancing the Seebeck coefficient and improving the thermoelectric performance of nitride-based devices by creating electron barriers and increasing phonon scattering.
Implementation Method 1
Introducing randomly located dislocations and high-density stacking faults, or microscopic alloy fluctuations in In-containing layers, which disrupt phonon propagation
Implementation Method 2
enhance the Seebeck coefficient through thermionic emission
Implementation Method 3
III-V nitride is a wide band gap semiconductor, and therefore remains a good unipolar semiconductor even at high temperatures above, e.g., around 1000 degrees Kelvin (K)
Data Source
AI summary
A method to suppress thermal conductivities of nitride films by using stacking faults and/or nano-scale In-composition fluctuation(s). Therefore, the present invention reduces thermal conductivity of nitride while keeping electrical conductivity high. In addition, In composition fluctuations can enhance the Seebeck coefficient through thermionic emission. The present invention further discloses a nitride based (e.g. GaN) thermoelectric lateral device with a short length.