Epitaxial AlN Template on Sapphire via Ga Concentration Gradient
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Solution Overview
Problem
The existing methods for growing AlN layers on sapphire substrates without lateral overgrowth face challenges in achieving a template with reduced threading dislocation density and good crystal morphology, often resulting in complex manufacturing processes and increased costs due to the need for etching and complicated growth control.
Innovation Solution
Dispersing a small amount of Ga atoms on the sapphire substrate surface before or at the start of AlN growth, with a Ga concentration distribution that maximizes at the interface between the substrate and the AlN layer, to facilitate stress distribution and prevent cracking, allowing for the growth of an AlN layer without lateral overgrowth and complex material supply methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a cyclic groove pattern is formed on the AlN underlying layer by photolithography and reactive ion etching, then the threading dislocation density is reduced significantly, but the manufacturing process becomes complex and the throughput decreases
Solution Approach 1:
The invention forms a Ga concentration gradient distribution in advance within the AlN layer before epitaxial growth of the GaN layer. This preliminary action creates a stress distribution that prevents threading dislocation formation during subsequent growth, eliminating the need for complex groove patterning processes while achieving low dislocation density.
Solution Approach 2:
The invention changes the chemical composition parameter by introducing Ga atoms with a specific concentration gradient (3×10^17 to 2×10^20 atoms/cm³) in the AlN layer. This parameter change modifies the stress state during epitaxial growth, enabling control of threading dislocation density without requiring structural modifications like groove patterns.
2Ease of manufacture
If the AlN layer is grown without lateral overgrowth method, then the manufacturing process is simplified, but it is difficult to achieve reduced threading dislocation density and good crystal surface morphology
Solution Approach 1:
The invention introduces a Ga concentration gradient parameter in the AlN layer that fundamentally changes the stress distribution during growth. This allows the AlN layer to be grown without lateral overgrowth while still achieving low threading dislocation density, as the Ga atoms prevent dislocation propagation through stress management.
Solution Approach 2:
The Ga atoms act as an intermediary substance within the AlN layer, mediating the stress between the sapphire substrate and the subsequently grown GaN layer. This intermediary presence prevents threading dislocation formation without requiring complex growth methods like lateral overgrowth.
3Reliability
If Ga atoms are dispersed on the sapphire substrate surface before AlN growth, then cracks are prevented and threading dislocation density is reduced, but the material supply method becomes more complex
Solution Approach 1:
The invention merges the Ga atom dispersion step with the AlN layer growth process. Instead of separate operations, the Ga atoms are supplied during the AlN growth itself, creating a combined process that achieves crack prevention and low dislocation density without significantly increasing process complexity.
Solution Approach 2:
The Ga atom supply is performed continuously or in a integrated manner during the AlN layer growth process, ensuring continuous stress management throughout the layer formation. This continuous action prevents crack development and dislocation formation without requiring additional discrete processing steps.
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 production of templates with no cracks, reduced threading dislocation density, and good crystal surface morphology, simplifying the manufacturing process and reducing costs while maintaining high crystal quality for GaN-family compound semiconductor layers.
Implementation Method 1
in a Ga concentration distribution in a depth direction perpendicular to the surface of the sapphire substrate in an internal region of the AlN layer excluding a near-surface region up to a depth of 100 nm from the surface of the AlN layer, which is obtained by secondary ion mass spectrometry, a position in the depth direction where the Ga concentration takes a maximum value is present in a near-interface region located between the interface of the sapphire substrate and a position at 400 nm spaced apart from the interface to the AlN layer side
Implementation Method 2
an AlN layer epitaxially grown on the sapphire substrate
Implementation Method 3
with a Ga concentration distribution that maximizes at the interface between the substrate and the AlN layer, to facilitate stress distribution and prevent cracking
Data Source
AI summary
The present invention provides a method for producing a template for epitaxial growth, the method including: a surface treatment step of dispersing Ga atoms on a surface of a sapphire substrate; and an AlN growth step of epitaxially growing an AlN layer on the sapphire substrate, wherein in a Ga concentration distribution in a depth direction perpendicular to the surface of the sapphire substrate in an internal region of the AlN layer excluding a near-surface region up to a depth of 100 nm from the surface of the AlN layer, which is obtained by secondary ion mass spectrometry, a position in the depth direction where the Ga concentration takes the maximum value is present in a near-interface region located between the interface of the sapphire substrate and a position at 400 nm spaced apart from the interface to the AlN layer side, and the maximum value of the Ga concentration is 3×1017 atoms/cm3 or more and 2×1020 atoms/cm3 or less.