VCSEL Tunnel Junction Structure for Heat and Light Loss Reduction
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Solution Overview
Problem
Vertical-cavity surface-emitting lasers face issues with heat dissipation and light loss due to the p-type semiconductor region, which has lower conductivity and higher light absorption compared to the n-type region, leading to increased contact resistance and forward voltage.
Innovation Solution
A vertical-cavity surface-emitting laser device is designed with a tunnel junction using heavily doped n-type semiconductor layers instead of p-type contact layers, featuring a recessed aperture in the p-type semiconductor layer and an etch stop layer to improve heat dissipation and reduce light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a p-type semiconductor region is used in the laser structure, then current injection is achieved, but heat dissipation is poor due to lower conductivity
Solution Approach 1:
The patent inverts the conventional structure by placing an n-type semiconductor layer instead of a p-type layer in contact with the electrode. This inversion allows the use of n-type material with superior thermal conductivity for heat dissipation while achieving current injection through a tunnel junction structure (p-type layer adjacent to n-type layer) rather than direct p-type electrode contact
Solution Approach 2:
The patent employs a composite structure combining p-type and n-type semiconductor layers in a tunnel junction configuration. The n-type layer provides excellent heat dissipation and low contact resistance, while the adjacent p-type layer enables current injection, creating a composite material system that leverages the advantages of both material types
2Power
If p-type dopants are used in the semiconductor region, then current flow is enabled, but light loss increases due to higher absorption
Solution Approach 1:
The patent inverts the conventional approach by using an n-type semiconductor layer in contact with the electrode instead of p-type material. Since n-type dopants absorb light less than p-type dopants, this inversion significantly reduces light loss while maintaining current flow capability through the tunnel junction mechanism
Solution Approach 2:
The patent introduces a tunnel junction as an intermediary structure between the electrode and the active region. This tunnel junction (comprising adjacent p-type and n-type layers) mediates current injection while allowing the bulk of the current path to traverse through the low-absorption n-type layer, thereby reducing overall light loss
3Power
If electrode contact is made with p-type contact layer, then current injection is achieved, but contact resistance is significantly higher
Solution Approach 1:
The patent inverts the conventional contact structure by making electrode contact with an n-type semiconductor layer instead of a p-type contact layer. Since n-type materials exhibit significantly lower contact resistance with standard electrode materials, this inversion directly addresses the high contact resistance problem while current injection is achieved through the adjacent p-type layer in the tunnel junction
Solution Approach 2:
The patent changes the key parameter of contact layer type from p-type to n-type. This parameter change fundamentally alters the electrical characteristics at the electrode interface, reducing contact resistance by an order of magnitude or more, while the overall current injection function is maintained through the tunnel junction structure
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
The design enhances heat dissipation performance, reduces contact resistance, and minimizes light loss by utilizing n-type cladding layers, resulting in improved electrical stability and efficiency.
Implementation Method 1
a heavily doped p-type semiconductor layer disposed between the active region and the upper n-type cladding layer; and a heavily doped n-type semiconductor layer disposed between the heavily doped p-type semiconductor layer and the upper n-type cladding layer to form a tunnel junction with the heavily doped p-type semiconductor layer
Implementation Method 2
Light generated in the active region is amplified between a lower mirror and an upper mirror
Implementation Method 3
Light generated in the active region is amplified between a lower mirror and an upper mirror, and is emitted to the outside through one of the mirrors
Implementation Method 4
an etch stop layer disposed between the active region and the heavily doped p-type semiconductor layer
Implementation Method 5
A side surface of the heavily doped p-type semiconductor layer is recessed inwardly to form an aperture
Data Source
Figure 1
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Figure 4~5
AI summary
A vertical-cavity surface-emitting laser element according to one embodiment comprises: a lower mirror; an upper mirror disposed above the lower mirror; an activated region located between the lower mirror and the upper mirror; a lower n-type cladding layer disposed between the activated region and the lower mirror; an upper n-type cladding layer disposed between the activated region and the upper mirror; a highly-concentrated doped p-type semiconductor layer disposed between the activated region and the upper n-type cladding layer; and a highly-concentrated doped n-type semiconductor layer disposed between the highly-concentrated doped p-type semiconductor layer and the upper n-type cladding layer to form a tunnel junction with the highly-concentrated doped p-type semiconductor layer.