Single-Crystal Bixbyite Oxide Layer for Aligned Growth on Si (100)
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Solution Overview
Problem
Current GaN chips require bonding to Si (100) substrates with wires, introducing failure modes and limiting device speed due to wire capacity, and existing methods for growing III-N materials on Si (100) substrates result in mismatched crystal orientations and poor quality layers.
Innovation Solution
A layered structure comprising a [100] oriented substrate with a [111] oriented crystalline bixbyite oxide layer, such as scandium oxide, followed by a metal-containing layer like GaN or Mo, which allows direct integration and higher quality growth without intermediate layers, reducing wiring needs and improving crystal alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to connect GaN chips to Si (100) substrates, then electrical connection is achieved, but device reliability decreases and speed is limited due to additional failure modes and wire capacity limitations
Solution Approach 1:
The patent merges the GaN chip and Si substrate into a single monolithic structure by growing GaN layers directly on the Si substrate through epitaxial growth. This eliminates the need for separate wire bonding interconnections, thereby improving reliability by removing additional failure modes and increasing device speed by eliminating wire capacity limitations.
Solution Approach 2:
The patent introduces a buffer layer structure as an intermediary between the Si substrate and GaN layer. This buffer layer, comprising multiple layers with gradually changing composition (e.g., AlGaAs, GaAs), mediates the lattice mismatch and thermal expansion differences between Si and GaN, enabling direct epitaxial growth and monolithic integration without wire bonding.
2Manufacturing precision
If conventional epitaxial growth methods are used on Si (100) substrates, then GaN layers can be grown, but crystal orientation mismatch occurs leading to poor layer quality
Solution Approach 1:
The patent changes the crystal orientation parameter of the substrate from conventional Si (100) to Si (111). This parameter change enables better crystal orientation matching for GaN growth, as GaN naturally grows in the [0001] polar direction which aligns well with the Si (111) surface, thereby improving layer quality while maintaining ease of manufacture through the use of commercially available Si substrates.
Solution Approach 2:
The patent applies local quality by creating a graded buffer layer structure where each layer has specific composition and thickness optimized for its local function. The buffer layers transition gradually from Si-based materials to GaN, with each layer locally tailored to manage lattice mismatch and dislocation density, achieving high overall crystal quality.
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 solution enables higher quality metal-containing layers on Si (100) substrates, facilitating direct integration of photonic and power devices, reducing failure modes, and enhancing device performance by eliminating wiring limitations and improving crystal quality.
Implementation Method 1
a crystalline bixbyite oxide layer in [111] orientation positioned, grown or deposited on the substrate; and a metal-containing layer crystallographically matched to the crystalline bixbyite oxide layer
Data Source
AI summary
A layered structure including a substrate in [100] crystal orientation, a crystalline bixbyite oxide layer in [111] orientation, and a metal-containing layer crystallographically matched to the crystalline bixbyite oxide layer. Also a method of fabricating a layered structure comprising steps to: epitaxially deposit a crystalline bixbyite oxide in [111] orientation on a substrate in [100] crystal orientation; and deposit a metal-containing layer on the crystalline bixbyite oxide layer.