Cleaved Facet GaN Laser Diodes on Semipolar Substrates
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Solution Overview
Problem
Existing semiconductor laser diodes grown on polar substrates face inefficiencies due to high polarization-induced electric fields and rough, dry-etched facets, leading to increased scattering losses and reduced reflectivity, while those grown on foreign substrates suffer from high defect densities and inferior performance.
Innovation Solution
The development of III-nitride edge-emitting laser diodes grown on semipolar {11-2n} substrates with cleaved m-plane or a-plane facets, created by scribing and applying force perpendicular to a nonpolar orientation, offering smoother and more reflective facets for reduced mirror loss and enhanced efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dry-etched facets are used in laser diodes grown on sapphire substrates, then the device structure can be manufactured, but scattering losses increase and reflectivity decreases
Solution Approach 1:
The patent replaces the mechanical dry-etching process with a chemical cleavage process. The laser diode structure is grown with a cleavable layer that naturally cleaves along smooth crystallographic planes when exposed to moisture or chemical agents, eliminating the need for mechanical etching and producing inherently smooth facets with high reflectivity and low scattering losses
2Adaptability or versatility
If laser diodes are grown on foreign substrates such as sapphire or SiC, then substrate availability is improved, but defect density increases and device performance deteriorates
Solution Approach 1:
The patent changes the crystallographic orientation parameter from conventional c-plane to semipolar or nonpolar orientations. This parameter change enables the growth of laser diodes on foreign substrates with reduced polarization-induced electric fields and lower defect densities, improving device performance while maintaining substrate availability benefits
3Ease of manufacture
If c-plane oriented substrates are used, then growth compatibility is maintained, but polarization-induced electric fields increase and efficiency decreases
Solution Approach 1:
The patent introduces asymmetry in the crystallographic orientation by transitioning from the symmetric c-plane orientation to semipolar or nonpolar orientations. This asymmetric orientation change reduces the strength of polarization-induced electric fields in the quantum wells, thereby reducing carrier separation effects and improving injection efficiency and overall device performance
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 results in lower threshold current density and improved device efficiency by reducing scattering losses and leveraging the theoretical benefits of semipolar orientations, such as lower effective hole masses in InGaN/GaN quantum wells.
Implementation Method 1
the III-nitride substrate is cleaved by creating a cleavage line along a direction substantially perpendicular to a nonpolar orientation of the III-nitride substrate, and then applying force along the cleavage line, to create one or more cleaved facets
Data Source
AI summary
A III-nitride edge-emitting laser diode is formed on a surface of a III-nitride substrate having a semipolar orientation, wherein the III-nitride substrate is cleaved by creating a cleavage line along a direction substantially perpendicular to a nonpolar orientation of the III-nitride substrate, and then applying force along the cleavage line to create one or more cleaved facets of the III-nitride substrate, wherein the cleaved facets have an m-plane or a-plane orientation.