GaN Capping Layer for AlN Buffer Oxidation Prevention
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Solution Overview
Problem
Existing methods for growing Group III nitride semiconductors often result in high threading dislocation density and N-polar surfaces due to oxidation of Al in the buffer layer during high-temperature heat treatment, leading to poor crystal quality and increased impurity incorporation.
Innovation Solution
A method involving the formation of a polycrystalline or amorphous AlN buffer layer with a capping layer to prevent oxidation, followed by high-temperature heat treatment without exposing the buffer layer, which reduces crystal nucleus density and threading dislocation density, and ensures a Ga-polar growth surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature heat treatment is performed on AlN buffer layer without protection, then crystal nucleus density is reduced and threading dislocation density is reduced, but Al in the buffer layer is oxidized forming Al oxide
Solution Approach 1:
A GaN capping layer is introduced as an intermediary protective barrier between the AlN buffer layer and the oxidizing atmosphere during high-temperature heat treatment. The capping layer prevents direct oxidation of Al in the buffer layer while allowing the heat treatment to proceed at temperatures above 1150°C to reduce crystal nucleus density and threading dislocation density.
Solution Approach 2:
The GaN capping layer is formed on the AlN buffer layer before the high-temperature heat treatment process. This preliminary protective action ensures that the buffer layer is shielded from oxidation before exposure to high temperatures, preventing Al oxide formation while enabling the subsequent dislocation reduction heat treatment.
2Manufacturing precision
If AlN buffer layer is heat-treated at high temperature without capping layer, then threading dislocation density is reduced, but N-polar surface is formed instead of Ga-polar surface
Solution Approach 1:
The GaN capping layer serves as a protective intermediary that maintains the Ga-polar surface orientation during high-temperature heat treatment. By preventing direct exposure of the AlN buffer layer to the vapor phase, the capping layer prevents N-polar surface formation and ensures the growth surface maintains its Ga-polar characteristics after heat treatment.
Solution Approach 2:
The GaN capping layer is deposited on the AlN buffer layer before heat treatment to establish a protective barrier that preserves surface polarity. This preliminary action ensures that when high-temperature heat treatment is applied to reduce threading dislocation density, the surface composition stability is maintained and N-polar surface formation is prevented.
3Manufacturing precision
If low temperature buffer layer is formed and then temperature is increased to GaN growth temperature, then fine crystals are formed, but fine crystals are decomposed and evaporated during temperature increase
Solution Approach 1:
The GaN capping layer acts as a protective intermediary that prevents decomposition and evaporation of fine crystals during temperature increase. By shielding the low-temperature buffer layer from direct exposure to high-temperature vapor phase, the capping layer allows safe temperature increase to GaN growth temperature while preserving the fine crystal structure.
4Manufacturing precision
If high-temperature heat treatment is performed without capping layer, then crystal quality is improved, but impurity incorporation increases due to N-polar surface
Solution Approach 1:
The GaN capping layer serves as a protective intermediary that prevents N-polar surface formation during high-temperature heat treatment. By maintaining the Ga-polar surface orientation through this protective barrier, the capping layer prevents the increased impurity incorporation that would otherwise occur on N-polar surfaces, thereby preserving both crystal quality and reliability.
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 significantly reduces threading dislocation density and maintains a uniform Ga-polar surface, enhancing the crystal quality and suitability of the semiconductor for device production.
Implementation Method 1
oxidation of Al in the buffer layer during high-temperature heat treatment
Implementation Method 2
high-temperature heat treatment without exposing the buffer layer, which reduces crystal nucleus density and threading dislocation density
Implementation Method 3
ensures a Ga-polar growth surface
Data Source
AI summary
Group III nitride semiconductor having reduced threading dislocation density and uniform Ga-polar surface is provided. Forming a capping layer on a buffer layer containing Al as an essential element at a temperature lower than a temperature at which an oxide of element constituting the buffer layer is formed. Heat treating the substrate having the buffer layer covered by the capping layer at a temperature higher than a temperature at which a crystal of body semiconductor grows without exposing the surface of the buffer layer. The substrate temperature is decreased to a temperature at which a crystal of the body semiconductor grows and the body semiconductor is grown.