AlGaInP Semiconductor Laser Asymmetric Cladding Structure
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Solution Overview
Problem
Semiconductor lasers face challenges in achieving high-temperature and high-optical output power characteristics due to electron overflow from the active layer into the p-type cladding layer, particularly for red lasers with lasing wavelengths around 640 nm, which requires improved bandgap difference and refractive index management without compromising reliability.
Innovation Solution
The semiconductor laser employs an asymmetric structure with an n-type cladding layer of (AlxnGa1-xn)0.5In0.5P and a p-type cladding layer of (AlxpGa1-xp)0.5In0.5P, where xn < xp, to optimize the Al composition ratio for enhanced optical confinement and reduced dopant diffusion, thereby improving high-temperature characteristics and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the Al composition ratio of the cladding layer is increased to improve high-temperature characteristics, then the bandgap difference between the active layer and cladding layer increases, suppressing electron overflow; however, the crystallinity of the cladding layer deteriorates and dopant diffusion increases, reducing reliability
Solution Approach 1:
The patent applies local quality by using different Al composition ratios in different regions: the n-type cladding layer uses (Al0.95Ga0.05)0.5In0.5P with x=0.95 to maximize bandgap difference and suppress electron overflow at high temperatures, while the p-type cladding layer uses (Al0.7Ga0.3)0.5In0.5P with x=0.7 to balance high-temperature performance with crystallinity and dopant diffusion control. This spatial differentiation of material composition resolves the contradiction between high-temperature characteristics and reliability.
2Temperature
If the bandgap difference between the active layer and cladding layer is increased to suppress electron overflow, then high-temperature characteristics improve; however, the refractive index difference changes, affecting optical confinement
Solution Approach 1:
The patent employs parameter changes by precisely controlling the Al composition ratio parameter in the cladding layers. The n-type cladding layer uses (Al0.95Ga0.05)0.5In0.5P and the p-type cladding layer uses (Al0.7Ga0.3)0.5In0.5P, where the Al composition ratio is optimized to simultaneously achieve sufficient bandgap difference for electron overflow suppression and appropriate refractive index difference for optical confinement. This parameter optimization resolves the contradiction between high-temperature characteristics and optical confinement stability.
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 configuration enhances high-temperature characteristics and reliability by reducing carrier overflow and internal loss, leading to lower threshold current, increased optical output power, and extended operational lifespan, while maintaining stability and refractive index differences.
Implementation Method 1
by using Al0.5In0.5P which is lattice-matched to a gallium arsenide (GaAs) substrate and having the largest bandgap among AlGaInP-based semiconductors to the p-type cladding layer and the n-type cladding layer to obtain a bandgap difference between the active layer and the cladding layers, electron overflow from the active layer to the p-type cladding layer is suppressed
Implementation Method 2
diffusion of a dopant (zinc (Zn), selenium (Se)) doped to the p-type cladding layer and the n-type cladding layer at a high concentration, i.e., 1×1018 cm−3 into the active layer is suppressed by providing an undoped layer between the active layer and the p-type cladding layer and between the active layer and the n-type cladding layer
Implementation Method 3
introducing a strained layer for inhibiting overflow of electrons between the active layer and the p-type cladding layer
Data Source
AI summary
An aluminium gallium indium phosphide (AlGaInP)-based semiconductor laser device is provided. On a main surface of a semiconductor substrate formed of n-type GaAs (gallium arsenide), from the bottom layer, an n-type buffer layer, an n-type cladding layer formed of an AlGaInP-based semiconductor containing silicon (Si) as a dopant, an active layer, a p-type cladding layer formed of an AlGaInP-based semiconductor containing magnesium (Mg) or zinc (Zn) as a dopant, an etching stopper layer, and a p-type contact layer are formed. Here, when an Al composition ratio x of the AlGaInP-based semiconductor is taken as a composition ratio of Al and Ga defined as (AlxGa1-x)0.5In0.5P, a composition of the n-type cladding layer is expressed as (AlxnGa1-xn)0.5In0.5P (0.9<xn<1) and a composition of the p-type cladding layer is expressed as (AlxpGa1-xp)0.5In0.5P (0.9<xp≤1), and xn and xp satisfy a relationship of xn<xp.