VCSEL Oxidation Structure to Protect DBR Thermal Conductivity

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Solution Overview

Problem

Conventional VCSEL device fabrication methods result in oxidation of DBR layers, leading to decreased thermal conductivity and operable wavelength bandwidth, causing higher thermal temperatures and unwanted wavelength shifts in the optically active region.

Innovation Solution

The introduction of sidewall spacers at intermediate steps in the fabrication process prevents oxidation in the DBR layers by forming spacers around the DBR layers and optically active region, ensuring that only the optically active region undergoes oxidation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If oxidation process is performed on VCSEL device structure, then optically active region is properly oxidized for device operation, but DBR layers also undergo oxidation causing decreased thermal conductivity and wavelength instability

Engineering Contradiction:

Improvedevice operational stabilityVSAvoidDBR layer thermal conductivity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

A sacrificial layer is introduced as an intermediary between the DBR layers and the oxidation environment. This sacrificial layer selectively protects the DBR layers from oxidation while allowing the optically active region to be properly oxidized. The sacrificial layer serves as a mediator that enables differential oxidation outcomes in different regions of the device structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The oxidation process is made selective to different regions of the device. The optically active region undergoes oxidation to achieve proper device operation, while the DBR layers are protected from oxidation to maintain their thermal conductivity and structural stability. This local differentiation of oxidation states resolves the contradiction between needing oxidation for operation and avoiding it for thermal stability.

Inventive Principle:

Principle #3Local quality

2Reliability

If oxidation process is performed on VCSEL device structure, then optically active region develops proper properties for lasing, but operable wavelength bandwidth decreases due to DBR layer oxidation

Engineering Contradiction:

Improvelasing functionalityVSAvoidwavelength bandwidth

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The sacrificial layer acts as a protective intermediary that prevents oxygen from reaching the DBR layers during the oxidation process. This selective protection maintains the DBR layers' optical properties and wavelength bandwidth while still allowing the optically active region to undergo necessary oxidation for lasing functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Different regions of the device are given different oxidation states appropriate for their function. The optically active region is oxidized to achieve proper lasing properties, while the DBR layers remain unoxidized to maintain broad wavelength bandwidth and optical reflectivity.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If oxidation process is performed on VCSEL device structure, then device fabrication is completed, but thermal temperature increases due to reduced thermal conductivity in oxidized DBR layers

Engineering Contradiction:

Improvefabrication completionVSAvoiddevice thermal temperature

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The sacrificial layer serves as a protective barrier that prevents oxidation of the DBR layers, thereby preserving their high thermal conductivity. This allows the device to be fabricated with proper oxidation of the optically active region while avoiding the thermal conductivity degradation that would otherwise occur in the DBR layers.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The oxidation process is localized only to the optically active region where it is needed for device operation, while the DBR layers are protected from oxidation to maintain their thermal management properties. This local quality control prevents overall device temperature increase.

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 approach maintains higher thermal conductivity and a more consistent wavelength output by preventing oxidation in the DBR layers, thus enhancing the operational stability and performance of the VCSEL device.

Implementation Method 1

performing an oxidation process with the first spacer in place to oxidize a peripheral region of the optically active layer

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS12237647B2Techniques for vertical cavity surface emitting laser oxidation

Publication Date: 2025.02.25 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Some embodiments relate to a method for forming a vertical cavity surface emitting laser (VCSEL) structure. The method includes forming an optically active layer over a lower reflective layer and forming an upper reflector over the optically active layer. A first spacer is formed along sidewalls of the upper reflector. An oxidation process is performed with the first spacer in place to oxidize a peripheral region of the optically active layer. A first etch process is performed on the lower reflective layer and the oxidized peripheral region, thereby forming a lower reflector and an optically active region.