Nitride Semiconductor Laser Light Confinement via Layer Composition
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Solution Overview
Problem
Nitride semiconductor laser devices with emission wavelengths between 430 nm and 540 nm face challenges due to low light confinement effects, leading to decreased internal and external quantum efficiency, increased threshold lasing current density, and higher operation voltage, primarily caused by refractive index differences and lattice mismatch between AlGaN and GaN layers.
Innovation Solution
A nitride semiconductor laser device structure is developed with specific composition ratios and thicknesses for AlGaN and InGaN layers, including an n-type AlGaN clad layer, GaN layer, first and second InGaN light guide layers, and p-type AlGaN layers, optimized to enhance light confinement and reduce lattice mismatch, along with a method for crystal growth that involves alternating supply of III group element sources and ammonia gases to form the InGaN light guide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Al composition ratio is increased in AlGaN material for the clad layer to make the refractive index difference sufficient, then the light confinement effect is improved, but the crystal lattice mismatch is increased causing generation of cracks and increase of operation voltage
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Al composition ratio in the n-type AlGaN clad layer to be 3% to 5% and the thickness to be 1.8 μm to 2.5 μm. These specific parameter ranges optimize the refractive index difference for sufficient light confinement while maintaining crystal lattice stability and avoiding crack generation.
Solution Approach 2:
The patent uses composite material structures by combining n-type AlGaN clad layer, GaN layer, InGaN light guide layers, and p-type AlGaN layers with specific composition ratios. This multi-layer composite structure achieves both sufficient light confinement and reduced lattice mismatch through careful material selection and composition control.
2Reliability
If the In composition ratio is increased in GaN material for the light guide layer to make the refractive index difference sufficient, then the light confinement effect is improved, but the crystal lattice mismatch is increased causing generation of cracks and increase of operation voltage
Solution Approach 1:
The patent applies parameter changes by controlling the In composition ratio in InGaN light guide layers to be within 3% to 6%. This specific range provides sufficient refractive index difference for light confinement while maintaining crystal lattice stability and preventing crack generation.
3Reliability
If the thickness of the n-type AlGaN clad layer is increased to improve light confinement, then the light absorption is reduced, but the operation voltage increases and cracks are generated
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the n-type AlGaN clad layer to be 1.8 μm to 2.5 μm. This specific thickness range provides sufficient light confinement and reduces light absorption while maintaining crystal lattice stability and avoiding crack generation.
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 optimized structure decreases operation voltage, increases external quantum efficiency, and reduces threshold lasing current density, resulting in improved power consumption and output power for nitride semiconductor laser devices within the specified wavelength range.
Implementation Method 1
the refractive index difference between AlGaN material for the clad layer and GaN material for the light guide layer generally used in the nitride-based semiconductor laser device becomes smaller as the wavelength becomes longer
Implementation Method 2
a method for forming the nitride semiconductor laser device preferably includes the steps of crystal-growing by supplying a III group element source containing In and Ga, a first ammonia gas, and a first carrier gas containing nitrogen and hydrogen
Data Source
AI summary
A nitride semiconductor laser device includes an n-type AlGaN clad layer, a GaN layer, a first InGaN light guide layer, a light-emitting layer, a second InGaN light guide layer, a nitride semiconductor intermediate layer, a p-type AlGaN layer, and a p-type AlGaN clad layer stacked in this order on a nitride semiconductor substrate, wherein the n-type AlGaN clad layer has an Al composition ratio of 3-5% and a thickness of 1.8-2.5 μm; the first and second InGaN light guide layers have an In composition ratio of 3-6%; the first light guide layer has a thickness of 120-160 nm and greater than that of the second light guide layer; and the p-type AlGaN layer is in contact with the p-type clad layer and has an Al composition ratio of 10-35% and greater than that of the p-type clad layer.