Semi-Polar Nitride Laser Diode Polarization Reduction
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Solution Overview
Problem
Semiconductor laser diodes based on group III nitrides face limitations in internal quantum efficiency due to spontaneous and piezoelectric polarizations, leading to reduced performance and wavelength shifts, especially for long-wavelength emission, and existing solutions like non-polar substrates are costly and size-constrained.
Innovation Solution
A semiconductor laser diode is fabricated using a semi-polar (11-22) plane formed by selectively growing group III nitride-based materials with a mask pattern, such as SiO2 or SiNx, on a c-plane substrate, which reduces the impact of polarization-induced effects and allows stable operation at high current densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a c-plane (0001) substrate is used for growing group III nitride-based semiconductor laser diode, then the manufacturing process is simpler and cost is lower, but spontaneous and piezoelectric polarizations cause quantum-confined Stark effect that deteriorates internal quantum efficiency and causes wavelength shift
Solution Approach 1:
The patent changes the crystal orientation parameter from c-plane (0001) to semi-polar (11-22) plane, which fundamentally alters the polarization characteristics. This parameter change reduces both spontaneous and piezoelectric polarization effects, thereby eliminating the quantum-confined Stark effect while maintaining manufacturing feasibility through selective growth methods
2Reliability
If a non-polar substrate is used to reduce polarization effects, then internal quantum efficiency is improved, but the substrate cost increases and severe size constraints are imposed
Solution Approach 1:
Instead of using expensive non-polar substrates with severe size constraints, the patent changes the growth plane parameter to semi-polar (11-22) plane on conventional substrates. This approach achieves similar polarization reduction benefits while maintaining substrate availability and cost-effectiveness through selective epitaxial growth
Solution Approach 2:
The patent introduces a mask pattern as an intermediary element that enables selective growth of the semi-polar (11-22) plane. This mask pattern acts as a mediator between the conventional substrate and the desired crystal orientation, allowing the system to achieve non-polar characteristics without requiring expensive non-polar substrates
3Illumination intensity
If high indium-content active layer is used to achieve long wavelength emission (500 nm or more), then the emission wavelength is extended, but band bending and non-uniform composition occur that reduce laser diode performance
Solution Approach 1:
The patent changes the crystal orientation parameter to semi-polar (11-22) plane, which reduces polarization effects and their adverse impact on band structure. This parameter change allows high indium-content active layers to maintain uniform composition and proper band alignment, enabling long wavelength emission without performance degradation
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 approach enhances the internal quantum efficiency and prevents wavelength shifts, enabling a stable semiconductor laser diode with improved performance without the cost and size constraints of non-polar substrates.
Implementation Method 1
A (11-22) plane, which is a semi-polar plane of a group III nitride, is formed by selectively growing a group III nitride-based material using a mask pattern (SiO2, SiNx)
Implementation Method 2
spontaneous polarization occurs in a c-plane (0001) direction that corresponds to a growth direction. In particular, when an LED having a representative InGaN/GaN quantum well structure is grown on a c-plane (0001), since a quantum-confined Stark effect (QCSE) is caused by piezoelectric fields due to an internal strain, caused by a lattice mismatch and the like
Implementation Method 3
spontaneous polarization occurs in a c-plane (0001) direction that corresponds to a growth direction
Data Source
AI summary
Provided are a semiconductor laser diode and a method for fabricating the same. The semiconductor laser diode includes a c-plane substrate, a group III nitride layer disposed on the c-plane substrate, and a first semiconductor layer, an active layer, and a second semiconductor layer disposed on the group III nitride layer in the stated order, wherein each of the first semiconductor layer and the second semiconductor layer is exposed to the outside of the semiconductor laser diode.