N-face GaN MOCVD Growth on Misoriented Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The growth of high-quality N-polar group III nitride films and heterostructures is challenging due to difficulties in achieving smooth surfaces and high In composition in InGaN, as well as low resistance p-type (Al,Ga,In)N:Mg films, which limits the development of efficient nitride-based electronic and optoelectronic devices.
Innovation Solution
A method for heteroepitaxial growth of high-quality N-face GaN, InN, and AlN films and their alloys using Metal Organic Chemical Vapor Deposition (MOCVD) on misoriented substrates, such as sapphire and silicon carbide, with specific misorientation angles and doping techniques to achieve smoother films and improved doping profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Ga-face is used for device fabrication, then device fabrication is enabled, but the growth temperature is limited and device types are restricted
Solution Approach 1:
The patent inverts the conventional approach by using N-face polarity instead of the traditional Ga-face polarity for group III nitride film growth. This inversion enables higher growth temperatures and expands device fabrication possibilities, particularly for InGaN alloys with high indium composition that require temperatures above 1000°C which are not achievable on Ga-face substrates.
2Reliability
If high Mg doping levels are used in (Al,Ga,In)N layers, then p-type conductivity is achieved, but polarity conversion from Ga-face to N-face occurs
Solution Approach 1:
The patent applies polarity inversion by growing N-face (Al,Ga,In)N layers instead of Ga-face layers. This allows high magnesium doping levels to be used while maintaining stable N-face polarity, preventing the polarity conversion that would otherwise occur and enabling reliable p-type conductivity in the cladding and barrier layers.
3Object-generated harmful factors
If N-face group III nitride films are grown, then opposite piezoelectric field direction is achieved, but growth difficulties and surface roughness occur
Solution Approach 1:
The patent employs parameter changes in the MOCVD growth process, including optimized temperature profiles (exceeding 1000°C), controlled precursor ratios, and specific pressure conditions, to achieve smooth N-face film growth. These parameter optimizations overcome the inherent growth difficulties and surface roughness issues associated with N-face polarity, enabling high-quality films with opposite piezoelectric field direction.
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 devices with enhanced charge transport properties, lower operating voltages, and improved carrier injection, allowing for the creation of efficient transistors, LEDs, and LDs with higher Indium composition InGaN alloys and higher p-type doping levels, overcoming limitations of Ga-polar growth.
Implementation Method 1
growing the N-face group III-nitride film on the growth surface by Metal Organic Chemical Vapor Deposition (MOCVD)
Data Source
AI summary
Methods for the heteroepitaxial growth of smooth, high quality films of N-face GaN film grown by MOCVD are disclosed. Use of a misoriented substrate and possibly nitridizing the substrate allow for the growth of smooth N-face GaN and other Group III nitride films as disclosed herein. The present invention also avoids the typical large (μm sized) hexagonal features which make N-face GaN material unacceptable for device applications. The present invention allows for the growth of smooth, high quality films which makes the development of N-face devices possible.