Group III Nitride LED Doping with Germanium or Tellurium
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Solution Overview
Problem
The growth of Group III nitride layers on silicon carbide or sapphire substrates leads to lattice mismatch and strain, causing defects and cracking in epitaxial layers, particularly due to the use of silicon dopants which increase strain and promote cracking, limiting the thickness of transition layers and efficiency of light-emitting diodes.
Innovation Solution
Incorporating n-type Group III nitride layers doped with germanium or tellurium, which have larger atomic and covalent radii than silicon, to reduce strain and allow for thicker transition layers, along with using chemical vapor deposition at temperatures below 900°C to form light-emitting diodes with improved efficiency and reduced cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon dopants are used in Group III nitride layers, then n-type conductivity is achieved, but strain increases and cracking is promoted
Solution Approach 1:
The patent changes the dopant parameter from silicon to germanium or tellurium. These alternative dopants have different atomic and covalent radii that better match the Group III nitride lattice, reducing the strain induced during doping while maintaining n-type conductivity. This parameter change resolves the contradiction between achieving conductivity and minimizing strain-induced cracking.
2Productivity
If thicker transition layers are used to reduce defects, then manufacturing yield improves, but strain increases causing cracking
Solution Approach 1:
The patent changes the dopant parameter to germanium or tellurium, which have atomic and covalent radii that better match the Group III nitride lattice structure. This reduces the strain per unit thickness, allowing thicker transition layers to be grown without reaching the critical strain threshold that causes cracking, thereby enabling higher manufacturing yield through reduced defect density.
3Reliability
If higher doping concentrations are used to improve conductivity, then electrical performance improves, but strain increases promoting cracking
Solution Approach 1:
The patent changes the dopant element from silicon to germanium or tellurium. These alternative dopants provide more effective doping efficiency, meaning that lower concentrations are required to achieve the same level of n-type conductivity. The lower required doping concentration, combined with the better lattice matching of Ge or Te, reduces the cumulative strain while maintaining improved electrical conductivity.
4Strength
If transition layers are made thinner to reduce strain, then cracking is reduced, but defect density increases
Solution Approach 1:
The patent changes the dopant parameter to germanium or tellurium, which have atomic and covalent radii that better match the Group III nitride lattice. This reduces the strain induced per unit thickness, allowing thicker transition layers to be grown without reaching the critical strain threshold for cracking. The thicker layers can then be grown with lower defect densities, simultaneously improving both cracking resistance and manufacturing precision.
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 use of germanium or tellurium as dopants in Group III nitride layers minimizes strain and allows for thicker, more efficient epitaxial layers with reduced defects, enhancing the performance and manufacturing yield of light-emitting diodes by reducing cracking and improving doping efficiency at lower temperatures.
Implementation Method 1
The growth of Group III nitride layers on silicon carbide or sapphire substrates leads to lattice mismatch and strain
Implementation Method 2
using chemical vapor deposition at temperatures below 900°C to form light-emitting diodes with improved efficiency and reduced cracking
Implementation Method 3
the Group III nitrides have relatively large band gaps, which gives them the capacity to emit relatively high energy photons, which in turn means that they can produce photons in the green, blue, violet, and ultraviolet portions of the electromagnetic spectrum
Data Source
AI summary
A light emitting diode is disclosed that is formed in the Group III nitride material system. The diode includes respective n-type and p-type layers for current injection and light emission. At least one n-type Group III nitride layer in the diode has dopants selected from the group consisting of elements with a larger atomic radius than silicon and elements with a larger covalent radius than silicon, with germanium and tellurium being exemplary.