Nitride Semiconductor Laser Layer Structure for Lower Absorption Loss
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Solution Overview
Problem
Semiconductor laser elements with nitride semiconductors face absorption losses due to p-type impurities, which reduce efficiency, particularly in higher light intensity regions.
Innovation Solution
A semiconductor laser element design featuring an undoped first part with a band gap energy increasing towards an electron barrier layer and a second part with a p-type impurity, where the ridge's lower end is positioned in the undoped p-side intermediate layer, reducing light absorption and enhancing optical confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If p-type impurity is doped to the p-side semiconductor layer, then electrical conductivity is improved, but light absorption loss increases
Solution Approach 1:
The p-side semiconductor layer is divided into multiple layers with different doping concentrations: a first p-type semiconductor layer with higher doping concentration for electrical conductivity, and a second p-type semiconductor layer with lower doping concentration to reduce light absorption. This segmentation allows each layer to optimize for its specific function.
Solution Approach 2:
Different regions of the p-side semiconductor layer are assigned different doping concentrations based on their functional requirements. The region closer to the active layer has lower doping to minimize absorption, while regions requiring higher conductivity have appropriate doping levels. This local optimization resolves the contradiction between conductivity and absorption loss.
2Reliability
If higher doping concentration is used in p-side semiconductor layer, then electrical conductivity increases, but slope efficiency decreases
Solution Approach 1:
The p-side semiconductor layer is segmented into multiple sub-layers with progressively decreasing doping concentrations. This allows the structure to maintain overall electrical conductivity while minimizing absorption losses in regions where light intensity is highest, thereby improving slope efficiency.
Solution Approach 2:
The doping concentration parameter is varied across different layers of the p-side semiconductor structure. By changing the doping parameter from high to low across the layers, the invention optimizes both electrical conductivity and optical transmission properties to improve slope efficiency.
3Productivity
If p-type impurity-containing layer is positioned closer to active layer, then hole injection efficiency improves, but absorption loss increases
Solution Approach 1:
The p-side semiconductor layer is divided into multiple layers positioned at different distances from the active layer, with doping concentrations optimized for each position. This segmentation enables hole injection efficiency while minimizing absorption losses by reducing doping in layers closer to the active layer.
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 design reduces absorption losses and increases efficiency by maintaining peak light intensity away from p-type impurity-containing layers, stabilizing the horizontal transverse mode and lowering drive voltage.
Implementation Method 1
an electron barrier layer disposed in contact with an upper face of the first part, containing a p-type impurity, and having a band gap energy that is larger than a band gap energy of the first part
Implementation Method 2
p-type impurities form deep-level traps, which cause light absorption to occur. For this reason, the higher the light intensity in the p-type impurity-containing layer, the larger the resulting absorption loss
Data Source
AI summary
A semiconductor laser element includes: an n-side semiconductor layer formed of a nitride semiconductor; an active layer disposed on or above the n-side semiconductor layer and formed of a nitride semiconductor; a p-side semiconductor layer disposed on the active layer, formed of a nitride semiconductor, and including: an undoped first part disposed in contact with an upper face of the active layer and comprising at least one semiconductor layer, an electron barrier layer disposed in contact with an upper face of the first part, containing a p-type impurity, and having a band gap energy that is larger than a band gap energy of the first part, and a second part disposed in contact with the upper face of the electron barrier layer and comprising at least one p-type semiconductor layer containing a p-type impurity; and a p-electrode disposed in contact with the upper face of the second part.