VCSEL Tunnel Junction Current Confinement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional VCSELs face issues with high parasitic resistance and capacitance due to ion-implantation processes, which affect current confinement and device performance, and are challenging to control, especially when dealing with thick semiconductor layers.
Innovation Solution
The VCSEL structure incorporates a first and second spacer layer with different conduction types, where only the second area of the first spacer layer is high-resistive, allowing current to flow through the second spacer layer without entering the second DBR, reducing parasitic resistance and capacitance, and using ion-implantation only in the second area to simplify the formation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion-implantation is applied to the entire p-type mirror to secure high resistance, then the resistance is improved, but the parasitic capacitance increases and device complexity increases
Solution Approach 1:
The patent applies ion-implantation selectively only to the second area of the first spacer layer surrounding the active layer, rather than the entire p-type mirror. This localized approach creates high resistance precisely where needed for current confinement while avoiding unnecessary implantation in other regions, thereby reducing parasitic capacitance and simplifying the device structure.
Solution Approach 2:
The spacer layer is divided into two distinct areas: a first area with lower resistance that allows current flow, and a second area with high resistance that confines current. This segmentation enables precise control of current paths while reducing overall device complexity by targeting only the necessary region for implantation.
2Reliability
If ion-implantation is applied to thick semiconductor layers, then resistance is improved, but controllability and reproducibility of ion distribution deteriorate
Solution Approach 1:
By restricting ion-implantation to the second area of the first spacer layer rather than thick mirror layers, the patent achieves better controllability and reproducibility of ion distribution. The localized implantation region allows precise control over ion penetration depth and concentration, ensuring consistent high resistance formation without the variability associated with implanting through thick layers.
3Device complexity
If current flows through the second DBR, then device structure is simplified, but parasitic resistance increases
Solution Approach 1:
The patent creates a localized high-resistance second area in the first spacer layer that acts as a current barrier, forcing current to flow exclusively through the active layer and first DBR. This selective resistance modification prevents current leakage into the second DBR, eliminating parasitic resistance while maintaining the overall device structure.
Solution Approach 2:
The second area of the first spacer layer serves as an intermediary element that mediates current flow between the electrode and the active layer. By introducing this high-resistance intermediary, the patent guides current through the desired path without directly modifying the second DBR 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
This approach reduces parasitic resistance and capacitance, enhances controllability and reproducibility of ion distribution, and maintains crystal quality, enabling high-speed operation with improved current confinement and optical characteristics.
Implementation Method 1
The second area of the first spacer layer may be heavily implanted with at least one of hydrogen (H) and oxygen (O)
Data Source
AI summary
A vertical cavity surface emitting laser diode (VCSEL) with a new structure is disclosed. The VCSEL of the invention provides the active layer, the first spacer layer, the tunnel junction, the second spacer layer burying the tunnel junction. Only the first spacer layer is ion-implanted to form a high-resistive region around the tunnel junction. The current injected into the second spacer layer is confined by the tunnel junction to reach the active layer, which reduces the increase of the parasitic resistance of the device. The high-resistive region around the tunnel junction reduces the parasitic capacitance of the device.