Surface Emitting Laser Contact Layer Segmentation
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Solution Overview
Problem
Surface emitting lasers face challenges in achieving high optical output while maintaining low drive voltage due to light absorption issues caused by impurities in contact layers, which increase resistance and drive voltage when the contact layer is made thinner to reduce absorption.
Innovation Solution
The design includes a first conductivity-type contact layer with a high impurity concentration made thin and a first conductivity-type semiconductor layer with a lower impurity concentration made thick, positioned on the DBR layer side, to minimize resistance and light absorption, allowing for both high optical output and low drive voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the contact layer is made thinner to reduce light absorption, then light absorption is suppressed, but the resistance value increases and drive voltage increases
Solution Approach 1:
The contact layer is divided into two distinct layers: a first contact layer with high impurity concentration for low resistance, and a second contact layer with low impurity concentration for low light absorption. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between resistance and light absorption.
Solution Approach 2:
Different regions of the contact structure are assigned different impurity concentrations based on their functional requirements. The first contact layer near the electrode has high impurity concentration for electrical conduction, while the second contact layer near the DBR has low impurity concentration to minimize light absorption. This local differentiation resolves the global contradiction.
2Loss of energy
If the contact layer is made thinner to reduce light absorption, then light absorption is suppressed, but the resistance value increases
Solution Approach 1:
The contact structure is segmented into two layers with different impurity concentrations. The first contact layer provides low resistance for reliable electrical contact, while the second contact layer minimizes light absorption. This segmentation allows both reliability and low light absorption to be achieved simultaneously.
Solution Approach 2:
The contact structure uses a composite of two materials with different impurity concentrations. This composite structure combines the electrical conductivity benefits of high-impurity material with the optical transparency benefits of low-impurity material, resolving the contradiction between resistance and light absorption.
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 effectively suppresses resistance and light absorption, enabling high optical output and low drive voltage in surface emitting lasers, particularly when using a semi-insulating substrate and epitaxial stacked structures.
Implementation Method 1
The contact layer serves for both a reduction in contact resistance between the electrode and the DBR layer and hole transportation from the electrode into a mesa part
Implementation Method 2
a vertical resonator including two distributed Bragg reflector layers that are opposed to each other
Implementation Method 3
a vertical resonator including two distributed Bragg reflector layers that are opposed to each other and an active layer, and allows laser light to oscillate
Data Source
AI summary
A surface emitting laser according to one embodiment of the present disclosure includes a mesa part including, in order, a first conductivity-type DBR layer, an active layer, a second conductivity-type DBR layer, and a second conductivity-type contact layer. The surface emitting laser further includes: a first conductivity-type contact layer provided in a region on the first conductivity-type DBR layer side in a positional relationship with respect to the mesa part; a first conductivity-type semiconductor layer that is disposed at a position opposed to the mesa part with the first conductivity-type contact layer interposed therebetween, and is in contact with the first conductivity-type contact layer, the first conductivity-type semiconductor layer having a lower impurity concentration than the first conductivity-type contact layer; a first electrode layer in contact with the first conductivity-type contact layer; and a second electrode layer in contact with the second conductivity-type contact layer.