Semiconductor Laser Guide Layer Band Gap Optimization

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Solution Overview

Problem

Conventional semiconductor lasers experience increased junction and operation voltages due to large band gap energy differences between layers, leading to reduced optical output efficiency and reliability, particularly when the thickness of guide layers is less than 100 nm.

Innovation Solution

A semiconductor laser structure with at least one guide layer thickness of 100 nm or more, where the band gap energy differences between the guide and active layers are 0.66 times or less of the differences between the clad and active layers, optimizing the band gap energies to reduce junction and operation voltages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the thickness of guide layers is increased to 100 nm or more, then the junction voltage and operation voltage are suppressed to be low, but the light intensity distribution is affected and slope efficiency is lowered

Engineering Contradiction:

Improvesemiconductor laser reliabilityVSAvoidslope efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent optimizes the band gap energy difference parameter between guide layer and active layer, setting it to 0.66 times or less of the difference between clad layer and active layer. This parameter optimization allows the guide layer thickness to be 100 nm or more while suppressing voltage rise and maintaining acceptable slope efficiency by balancing electron-hole density and quasi-Fermi level slope.

Inventive Principle:

Principle #35Parameter changes

2Strength

If the band gap energy difference between guide layer and active layer is large, then the optical confinement is improved, but the junction voltage and operation voltage elevate

Engineering Contradiction:

Improveoptical confinementVSAvoidoperation voltage

Core Design Contradiction:

StrengthVSPower

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies different band gap energy differences to different regions: the guide layer has a smaller band gap energy difference (0.66 times or less) compared to the clad layer, creating a gradient structure. This local quality differentiation allows optimal optical confinement in the guide layer while minimizing voltage rise, and stronger confinement in the clad layer.

Inventive Principle:

Principle #3Local quality

3Strength

If the band gap energy difference between guide layer and active layer is large, then the optical confinement is improved, but the electrical conversion efficiency is reduced

Engineering Contradiction:

Improveoptical confinementVSAvoidelectrical conversion efficiency

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

4Power

If the guide layer thickness is less than 100 nm, then the junction voltage is low, but the electron-hole density balance is insufficient and reliability is lowered

Engineering Contradiction:

Improvejunction voltageVSAvoidsemiconductor laser reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7289546B1Semiconductor laser having an improved stacked structure

Publication Date: 2007.10.30 MITSUBISHI ELECTRIC CORP

AI summary

An n-type first cladding layer, a first guide layer, a first enhancing layer, an active layer, a second enhancing layer, a second guide layer, and a p-type second cladding layer are sequentially stacked on an n-type GaAs substrate. The thickness of each of the first guide layer and the second guide layer is 100 nm or more. In such a semiconductor laser, the difference between the Eg (band gap energy) of the first guide layer and the Eg of the active layer (or the difference between the Eg of the second guide layer and the Eg of the active layer) is made 0.66 times or less of the difference between the Eg of the first cladding layer and the Eg of the active layer (or the difference between the Eg of the second cladding layer and the Eg of the active layer).