Liquid Phase Epitaxy GaN Pulsed Nitrogen Plasma
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Solution Overview
Problem
Current methods for growing bulk GaN films are hindered by high pressure and temperature requirements, leading to slow growth rates and high costs, while existing epitaxy techniques face challenges with spontaneous nucleation and contamination issues.
Innovation Solution
The use of pulsed nitrogen plasma in liquid phase epitaxy (LPE) to control nitrogen concentration and prevent crust formation on molten Group III metals, allowing for epitaxial growth of GaN at low pressures without hazardous precursors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high pressure and temperature methods are used to grow bulk GaN, then crystalline quality is improved, but growth rate decreases and cost increases
Solution Approach 1:
The patent utilizes liquid phase epitaxy where GaN grows from a liquid Ga melt rather than from vapor or solid phases. This phase transition approach allows growth at lower temperatures (below GaN melting point of 2500°C) while maintaining high crystalline quality, thereby resolving the contradiction between quality and growth rate/cost
Solution Approach 2:
The patent changes the pressure parameter from high pressure (traditional bulk growth) to low pressure (1-100 atm), and controls temperature to maintain Ga in liquid state. These parameter changes enable faster growth rates while preserving crystalline quality through the liquid phase growth mechanism
2Productivity
If continuous plasma exposure is used to grow GaN films, then growth rate is improved, but crust formation occurs on molten metal surface
Solution Approach 1:
The patent employs pulsed plasma exposure with alternating on/off cycles instead of continuous plasma. This periodic action allows the molten Ga surface to periodically recover from nitrogen saturation, preventing crust formation while maintaining high growth rates during the plasma on-periods
Solution Approach 2:
The patent dynamically adjusts plasma power and pulse duration to control nitrogen flux into the molten Ga. This dynamic control prevents excessive nitrogen concentration that causes crust formation, while ensuring sufficient nitrogen supply for high growth rates, thus resolving the contradiction between growth rate and uniformity
3Reliability
If traditional epitaxy techniques are used, then crystalline quality is improved, but contamination from precursors occurs
Solution Approach 1:
The patent replaces chemical precursor-based epitaxy (MOCVD, MBE) with plasma-based liquid phase epitaxy. This substitution eliminates organic metal precursors that cause carbon contamination, using instead reactive nitrogen plasma and liquid Ga, thereby achieving high crystalline quality without precursor contamination
Solution Approach 2:
The patent uses nitrogen plasma in a controlled atmosphere to provide nitrogen atoms for GaN growth without introducing carbon-containing precursors. This inert/controlled environment approach prevents carbon contamination while maintaining high crystalline quality through pure nitrogen supply from plasma
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 enables rapid, cost-effective growth of GaN films with improved uniformity and reduced contamination, achieving growth rates comparable to MOCVD and faster than traditional plasma-assisted electroepitaxy, while maintaining high crystalline quality.
Implementation Method 1
exposing the liquid phase Group III metal or alloy thereof to a pulsed Group V plasma to form the epitaxial layer
Implementation Method 2
pulsed nitrogen plasma in liquid phase epitaxy (LPE) to control nitrogen concentration
Implementation Method 3
One of the main challenges in LP-LPE of GaN is to prevent spontaneous nucleation of GaN
Implementation Method 4
liquid phase epitaxy (LPE) to control nitrogen concentration and prevent crust formation on molten Group III metals, allowing for epitaxial growth of GaN
Data Source
AI summary
Provided herein are methods of performing liquid phase epitaxy (LPE) of III-V compounds and alloys at low pressures using pulsed nitrogen plasma to form an epitaxial layer e.g. on a substrate. The pulse sequence of plasma (with on and off time scales) enables LPE but avoids crust formation on top of molten metal. The concentration of nitrogen inside the molten metal is controlled to limit spontaneous nucleation.