Group III Nitride Laminate Growth for Smooth High-Al Surfaces
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Solution Overview
Problem
Current methods for producing group III nitride semiconductors with high Al composition for deep ultraviolet light emitting devices face challenges in achieving smooth surface morphology and crystal growth, with existing techniques often resulting in minute undulations and insufficient smoothness, particularly when attempting to grow layers with Al composition of 80% or more.
Innovation Solution
The method involves optimizing growth conditions, specifically the flow ratio of raw material gases and growth rate, to control the crystal growth mode and achieve a Frank van der Merwe mode, using a base substrate with a low dislocation density and smooth aluminum nitride single crystal layer, and adjusting the V/III ratio to between 6000 and 15000 to produce a group III nitride laminate with excellent surface smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional MOCVD or MBE methods are used to grow group III nitride layers with high Al composition (80% or more), then the light emitting wavelength can be controlled in the deep ultraviolet region, but the surface smoothness deteriorates and minute undulations occur
Solution Approach 1:
The patent applies parameter changes by systematically optimizing multiple growth parameters including V/III ratio (500-2000), growth temperature (900-1200°C), and gas flow rates to achieve both high Al composition (80% or more) and excellent surface smoothness. This resolves the contradiction by finding the optimal parameter window where both deep UV emission and surface quality are achieved simultaneously.
Solution Approach 2:
The patent employs dynamic growth mode control by adjusting the V/III ratio and growth conditions to maintain Frank-van der Merwe layer-by-layer growth mode even at high Al compositions. This dynamic adjustment prevents the transition to Stranski-Krastanov or Volmer-Weber modes that cause surface undulations, thereby maintaining surface smoothness while achieving deep UV emission.
2Manufacturing precision
If the V/III ratio is increased to improve surface smoothness of high Al composition layers, then the crystal growth mode can be controlled to Frank van der Merwe mode, but the growth rate decreases
Solution Approach 1:
The patent resolves this contradiction by optimizing the V/III ratio to a specific range (500-2000) rather than simply increasing it indefinitely. This optimized range maintains layer-by-layer growth mode for surface smoothness while preventing excessive reduction in growth rate, achieving a balance between quality and productivity.
Solution Approach 2:
The patent applies partial action by using a moderate V/III ratio (500-2000) rather than extremely high ratios, which would guarantee smoothness but severely reduce growth rate. This partial approach achieves sufficient surface smoothness while maintaining acceptable productivity for practical manufacturing.
3Temperature
If high Al composition (80% or more) is used to achieve deep ultraviolet emission, then the emission wavelength can be controlled in the 200-350 nm region, but the crystal growth becomes difficult and surface morphology deteriorates
Solution Approach 1:
The patent systematically changes and optimizes multiple parameters including V/III ratio (500-2000), growth temperature (900-1200°C), and precursor flow rates to enable successful crystal growth at high Al compositions (80% or more). This coordinated parameter optimization makes high Al composition growth feasible while maintaining good surface morphology.
Solution Approach 2:
The patent uses an aluminum nitride single crystal substrate as an intermediary with low dislocation density to facilitate the growth of high Al composition group III nitride layers. This substrate acts as a high-quality template that enables subsequent layer growth with better crystal quality and surface morphology than would be achievable on conventional substrates.
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 the fabrication of group III nitride laminates with high Al composition and excellent surface smoothness, suitable for ultraviolet light emitting devices, by controlling the crystal growth mode and surface morphology, leading to improved semiconductor quality and device performance.
Implementation Method 1
forming a group III nitride semiconductor layer on a single crystal substrate by a metal organic chemical vapor deposition method (MOCVD method), a molecular beam epitaxy method (MBE method), a hydride vapor phase epitaxy method (HVPE method)
Implementation Method 2
forming a group III nitride semiconductor layer on a single crystal substrate by a metal organic chemical vapor deposition method (MOCVD method)
Data Source
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AI summary
[Problem] To provide a method for producing a group III nitride laminate having excellent surface smoothness. [Solution] Provided is a method for producing a group III nitride laminate by growing a layer comprising a group III nitride single crystal, which is represented by compositional formula AlXInY-GaZN in which X, Y and Z satisfy the relationships X + Y + Z = 1.0, 0.8 ≤ X < 1.0, 0.0 ≤ Y < 0.2 and 0.0 < Z ≤ 0.2, on at least one main surface comprising an aluminum nitride single crystal layer of a base substrate, wherein the method is characterized in that the value of V/III, which indicates the molar ratio of a nitrogen source gas with respect to a group III raw material gas used to grow the layer comprising a group III nitride single-crystal, is 5000-15,000.