Semiconductor Laser Element With Segmented P-Clad Layer

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Solution Overview

Problem

Semiconductor laser elements with nitride semiconductors face increased absorption losses due to p-type impurities forming deep-level traps, leading to reduced efficiency, particularly in high light intensity regions.

Innovation Solution

A semiconductor laser element design featuring a p-side semiconductor layer with an undoped first part, an electron barrier layer, and a second part with p-type impurities, where the lower end of the ridge is positioned in the undoped p-side composition graded layer and intermediate layer, reducing light intensity in p-type impurity-containing layers and minimizing absorption losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If p-type impurities are doped to the p-side semiconductor layer, then electrical conductivity is improved, but absorption loss increases due to deep-level traps

Engineering Contradiction:

Improveelectrical conductivityVSAvoidabsorption loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The p-side semiconductor layer is divided into multiple regions with different doping concentrations: a first region with lower p-type impurity concentration and a second region with higher p-type impurity concentration. This segmentation allows the first region to have lower absorption loss while the second region provides sufficient electrical conductivity, resolving the contradiction between conductivity and absorption loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the p-side semiconductor layer are assigned different local properties: the first region has lower impurity concentration optimized for reducing absorption loss, while the second region has higher impurity concentration optimized for electrical conductivity. This local quality differentiation allows each region to perform its specific function optimally.

Inventive Principle:

Principle #3Local quality

2Power

If light intensity in p-type impurity-containing layer is increased, then output power is improved, but absorption loss increases proportionally

Engineering Contradiction:

Improveoutput powerVSAvoidabsorption loss

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The optical path is segmented through the layered structure where light passes through the first region with lower impurity concentration (lower absorption) before reaching the second region. This segmentation of the optical path reduces cumulative absorption loss while maintaining sufficient light intensity for power output.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first region acts as an intermediary layer between the active layer and the second region, providing a transition zone with moderate absorption characteristics that allows light to pass through with reduced loss before entering the high-conductivity second region.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If thickness of p-side clad layer is reduced, then absorption loss is decreased, but optical confinement is weakened

Engineering Contradiction:

Improveabsorption lossVSAvoidoptical confinement

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

The p-side clad layer is segmented into multiple regions with different impurity concentrations, allowing the overall layer to maintain sufficient thickness for optical confinement while specific sub-regions have lower impurity concentrations to reduce absorption loss in the optical path.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the p-side clad layer have different local qualities: regions where light passes through have lower impurity concentration to minimize absorption, while other regions maintain higher concentration or sufficient thickness to ensure optical confinement and electrical performance.

Inventive Principle:

Principle #3Local quality

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 design enhances optical confinement, stabilizes the transverse mode, and increases efficiency by reducing absorption losses and drive voltage, as demonstrated by improved slope efficiency and I-V characteristics.

Implementation Method 1

the electron barrier layer... having a band gap energy that is larger than a band gap energy of the first part

Methodology Applied

Scientific EffectBand gap energy difference:

Implementation Method 2

the first part includes an undoped p-side composition graded layer in which a band gap energy increases towards the electron barrier layer

Methodology Applied

Scientific EffectOptical confinement:

Data Source

PatentEP3683907B1Semiconductor laser element and method for manufacturing the same

Publication Date: 2023.01.25 NICHIA CORP

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Figure 2A
Figure 2B

AI summary

A semiconductor laser element (100) includes an n-side semiconductor layer (2), an active layer (3), and a p-side semiconductor layer (4). A least a portion of the p-side semiconductor layer (4) forms a ridge (4a) projecting upward. The p-side semiconductor layer (4) includes an undoped first part (41), an electron barrier layer (42) containing a p-type impurity and having a larger band gap energy than the first part (41), and a second part (43) having at least one p-type semiconductor layer. The lower end of the ridge (4a) is positioned at the first part (41).