Surface-Emitting Laser Structure for Uniform Current Injection
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Solution Overview
Problem
Existing surface-emitting lasers using GaN-based materials face challenges in achieving uniform current density distribution due to high resistance of ITO and p-GaN layers, leading to non-uniform current injection and difficulty in obtaining stable single-mode operation.
Innovation Solution
A surface emitting laser design incorporating a first p-type semiconductor layer with a smaller band gap and a second p-type semiconductor layer with a larger band gap, forming a two-dimensional hole gas (2DHG) at their interface, allowing current injection through both the upper surface and side wall, thereby enhancing lateral current distribution uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thin ITO layer is used to reduce light absorption, then light transmission is improved, but current injection uniformity deteriorates due to high lateral resistance
Solution Approach 1:
The invention transitions from single-top-surface current injection to multi-dimensional current injection by enabling current flow through both the upper surface and the side wall of the resonator. The conductive layer is extended to contact the side wall, creating a two-path current injection geometry that resolves the contradiction between thin ITO for light transmission and sufficient current distribution.
Solution Approach 2:
The side wall conductive layer acts as an intermediary current path that bypasses the limitation of thin ITO lateral resistance. By providing an additional current injection route through the side wall, the system achieves uniform current distribution without requiring thicker ITO that would absorb light.
2Power
If a large aperture diameter is used to increase active layer area, then output power is improved, but current injection uniformity deteriorates due to ITO resistance
Solution Approach 1:
The side wall current injection path provides an additional dimensional route for current distribution. This allows large aperture diameters to be used for higher output power while maintaining current uniformity through the distributed side wall contact, overcoming the limitation of top-surface-only injection where current spreads laterally through high-resistance ITO.
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 achieves higher uniformity of current density within the resonator, reducing resistance and facilitating stable single-mode operation by confining light in the lateral direction, thus enhancing optical performance.
Implementation Method 1
forming a two-dimensional hole gas (2DHG) at their interface
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A surface emitting laser includes: a first reflector; a second reflector; a resonator between the first reflector and the second reflector, the resonator including an active layer; and a conductive layer. The resonator further includes: a first layer including a first p-type semiconductor layer having a first band gap, the first layer having a first face contacting the conductive layer and a second face opposite to the first face; and a second layer including a second p-type semiconductor layer having a second band gap larger than the first band gap, the second layer between the first layer and the active layer. The second p-type semiconductor layer contacts the second face of the first layer. The conductive layer contacts at least a part of the first face of the first layer and an interface between the first layer and the second layer.