Quantum Well Green Laser Structure for Uniform Hole Injection
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Solution Overview
Problem
Nitride semiconductor laser devices face challenges such as high p-type semiconductor activation energy, low hole concentration and mobility, uneven hole injection, and increased thermal loss, leading to inefficiencies and reduced performance, particularly in green laser devices.
Innovation Solution
A semiconductor green laser is designed with a specific structure comprising a substrate, lower and upper limiting layers, waveguide layers, and active layers composed of well and barrier layers with tailored electron effective mass, spontaneous polarization, and band gap distributions, along with a thermal expansion coefficient, dielectric constant, and elasticity coefficient gradients to enhance thermal management and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high element In is used in the quantum well to achieve green laser emission, then the laser wavelength can be tuned to green region, but thermal stability deteriorates and InN phase separation occurs leading to poor crystal quality
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratio of InGaN and the thickness of quantum well layers to optimize the balance between achieving green laser emission and maintaining thermal stability. By adjusting these parameters, the patent avoids InN phase separation while achieving the desired wavelength.
2Ease of operation
If p-type semiconductor is used for hole injection, then hole injection can be achieved, but activation energy is high and hole concentration is low leading to uneven hole injection
Solution Approach 1:
The patent applies local quality by creating composition gradients in the InGaN layers, where the indium composition varies spatially to optimize hole injection characteristics in different regions. This gradient structure improves hole injection uniformity by reducing the activation energy barrier in critical regions while maintaining overall device performance.
3Illumination intensity
If high current density is used to achieve laser output, then brightness increases, but electron leakage increases and Auger recombination becomes more severe leading to Droop effect
Solution Approach 1:
The patent converts the harmful Auger recombination effect into a beneficial mechanism by engineering the quantum well structure and composition profile to enhance radiative recombination efficiency. The optimized InGaN composition and quantum well design promote direct radiative transitions while suppressing non-radiative Auger processes, thereby reducing electron leakage and mitigating the Droop effect at high current densities.
4Power
If quantum well structure is used to achieve laser emission, then light amplification can be realized, but polarization electric field enhances hole injection barrier and causes hole overflow
Solution Approach 1:
The patent applies asymmetry by designing asymmetric quantum well structures with different barrier heights and widths on either side of the well. This asymmetric design allows the structure to maintain strong light amplification through optimized optical confinement while simultaneously reducing the hole injection barrier by creating favorable potential gradients that facilitate hole transport and prevent hole overflow.
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 proposed semiconductor green laser achieves improved hole injection efficiency, reduced thermal stress, enhanced carrier uniformity, increased optical power, and improved slope efficiency, addressing the deficiencies in prior nitride semiconductor laser devices.
Implementation Method 1
The active layer may be a quantum well composed of well layers and barrier layers
Implementation Method 2
A laser is generated by carriers undergoing excited radiation, a spectral full width at half maximum (FWHM) is small, a brightness is very high
Implementation Method 3
lower waveguide layer, an active layer, an upper waveguide layer
Data Source
AI summary
The present disclosure provides a semiconductor green laser. The semiconductor green laser, from bottom to top, comprising a substrate, a lower limiting layer, a lower waveguide layer, an active layer, an upper waveguide layer, and an upper limiting layer. The active layer is a quantum well composed of well layers and barrier layers. Each of the well layers includes any one of AlInGaN, AlInN, AlGaN, AlN, InN, InGaN, and GaN, or any combination thereof. Each of the barrier layers includes any one of AlInGaN, AlInN, AlGaN, AlN, InN, InGaN, and GaN, or any combination thereof. An electron effective mass of each of the well layers is less than an electron effective mass of each of the barrier layers. A spontaneous polarization coefficient of each of the well layers is less than a spontaneous polarization coefficient of each of the barrier layers.