GaN Substrate with Disoriented Stripes for Non-Absorbing Mirrors
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Solution Overview
Problem
Existing gallium nitride substrates for epitaxial growth in semiconductor light emitters suffer from Catastrophic Optical Mirror Damage due to light absorption in laser diode facets, making it difficult to achieve non-absorbing mirrors, especially with methods like quantum well intermixing which is not effective for gallium nitride.
Innovation Solution
A substrate with a growth surface comprising sets of neighbouring flat surfaces, where the longer edges are parallel and disoriented relative to specific crystallographic planes, allowing for controlled lateral composition of the active layer and enabling the fabrication of semiconductor light emitters with non-absorbing mirrors and broadened emission spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional monocrystalline GaN substrates with uniform orientation are used for epitaxial growth, then the fabrication process is simple, but Catastrophic Optical Mirror Damage occurs due to light absorption in laser diode facets
Solution Approach 1:
The substrate surface is segmented into multiple regions with different orientations relative to the crystallographic planes. Specifically, the substrate includes first regions oriented at a first angle and second regions oriented at a second angle relative to the (0001) plane, creating spatially distinct zones that perform different functions in the laser diode structure.
Solution Approach 2:
Different regions of the substrate are given different local properties through varying their crystallographic orientation. The first regions and second regions have different angles relative to the (0001) plane, which results in different material properties and optical characteristics in the epitaxially grown layers, allowing one region to serve as the active layer while another serves as a non-absorbing mirror.
2Object-affected harmful factors
If quantum well intermixing is used to create non-absorbing mirrors in GaInAlAsP laser structures, then the mirror absorption is reduced, but the method is cumbersome and not practical for gallium nitride
Solution Approach 1:
The substrate is prepared in advance with regions of different orientations before epitaxial growth begins. This preliminary orientation differentiation allows the subsequent epitaxial growth to naturally produce layers with different compositions and properties in different regions, eliminating the need for post-growth processing steps like quantum well intermixing.
Solution Approach 2:
The crystallographic orientation angle is changed across different regions of the substrate. By varying this geometric parameter, the invention achieves different material properties and optical characteristics without requiring complex chemical or thermal processing steps, thereby simplifying the overall fabrication process.
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 allows for the effective control of the active layer composition, enabling the easy and economical fabrication of semiconductor light emitters with improved laser structures, including non-absorbing mirrors and superluminescent diodes with broadened emission spectra, and laser diode arrays emitting at various wavelengths.
Implementation Method 1
A substrate for epitaxial growth made of a gallium nitride crystal, having one surface prepared for the epitaxial growth
Data Source
AI summary
A surface of a substrate consists of a plurality of neighboring stripes. Longer edges of the flat surfaces are parallel one to another and planes of these surfaces are disoriented relatively to the crystallographic plane of gallium nitride crystal defined by Miller-Bravais indices (0001), (11-22) or (11-20). The disorientation angle of each of the flat surfaces is between 0 and 3 degrees and is different for each pair of neighboring flat surfaces. The substrate according to the invention allows epitaxial growth of a layered AlInGaN structure by a MOCVD or MBE method which allow to obtain a non-absorbing mirrors laser diode emitting a light in the wavelength from 380 to 550 nm.