VCSEL Current Constriction for LiDAR Beam Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor light-emitting elements face challenges in achieving high power while maintaining beam control in the far field and preventing voltage increases, particularly in vertical cavity surface-emitting lasers (VCSELs) used for time-of-flight LiDAR applications.
Innovation Solution
A semiconductor light-emitting element with a structure comprising a substrate, reflectors, a resonator cavity, and a tunnel junction portion, featuring a first current constriction portion with an oxidation constriction layer and a second current constriction portion with a narrower width, which controls current density distribution to enhance beam control and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the light-emitting diameter is increased to achieve high power, then the power output is improved, but the current density distribution becomes unbalanced and beam control deteriorates
Solution Approach 1:
The patent applies local quality by creating different current constriction structures at different locations within the light-emitting region. The first current constriction portion is positioned at the center while the second current constriction portion is positioned at the periphery, with each having different dimensions and current constriction strengths. This allows the center and peripheral regions to have optimized current density distributions independently, maintaining beam control while enabling high power output through the increased light-emitting diameter.
2Reliability
If ion implantation is used to form current constriction structure, then the peripheral portion resistance is increased, but the element voltage increases due to thick current path
Solution Approach 1:
The patent transitions from a single-layer current constriction approach to a multi-layer vertical structure. By stacking the first current constriction portion (with oxidation constriction layer) and the second current constriction portion (with tunnel junction) at different vertical positions and depths, the current path is optimized in the vertical dimension. This allows current to flow through thinner, lower-resistance paths while still achieving effective current constriction at the periphery, thereby reducing element voltage while maintaining reliability.
3Power
If substrate rear face emission is used, then current density can be increased, but light absorption by substrate prevents high power achievement
Solution Approach 1:
The patent inverts the conventional emission direction by using substrate front face emission instead of rear face emission. The light is emitted from the front face of the substrate through the tunnel junction portion, away from the substrate bulk. This inversion avoids the light absorption problem that occurs in rear face emission where light must pass through the substrate, enabling high power achievement while maintaining increased current density through the optimized current constriction structures.
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 allows for high-power operation with improved beam control in the far field and reduced voltage increase, enhancing ranging accuracy and measurable distance in LiDAR devices.
Implementation Method 1
a first current constriction portion configured with an oxidation constriction layer
Implementation Method 2
a second current constriction portion including the tunnel junction portion
Data Source
AI summary
A semiconductor light-emitting element having a structure in which a substrate, a first reflector, a resonator cavity including an active layer, a second reflector and a tunnel junction portion are stacked in this sequence, comprising: a first current constriction portion configured with an oxidation constriction layer; and a second current constriction portion including the tunnel junction portion, wherein a width d2 of the second current constriction portion is smaller than a width d1 of the first current constriction portion.