Semiconductor Laser Layer Gradients to Reduce Band Spike Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor laser elements experience high carrier loss due to band spikes at heterointerfaces, leading to increased threshold current and current density, which affects the efficiency and wavelength stability of laser emission.
Innovation Solution
The semiconductor laser element incorporates a p-side semiconductor layer with a first composition gradient layer made of InxGa1-xN and a second composition gradient layer made of AlyGa1-yN, along with an intermediate layer, to gradually change the band gap energy and reduce the influence of band spikes, thereby minimizing carrier loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional heterostructure interfaces are used in semiconductor laser elements, then device structure is simple, but band spikes occur at interfaces causing high carrier loss and increased threshold current
Solution Approach 1:
The patent divides the conventional single interface heterostructure into multiple graded composition layers (InGaN layers with gradually changing In composition ratios) between the active layer and p-type cladding layer. This segmentation eliminates abrupt band discontinuities that cause carrier loss while maintaining structural organization through systematic composition gradients.
Solution Approach 2:
The patent applies local quality by creating regions with different In composition ratios (x1, x2, x3 where x1 > x2 > x3) at specific positions within the p-side semiconductor layer. Each local region has optimized composition to gradually reduce band gap differences, minimizing carrier loss at each interface while maintaining overall device functionality.
2Reliability
If graded composition layers are added to reduce band spikes, then carrier loss is reduced, but device structure becomes more complex
Solution Approach 1:
The patent systematically changes the In composition ratio parameter (x) across multiple layers to create gradual band gap transitions. By controlling the composition parameter x1 > x2 > x3, the patent achieves reduced carrier loss and improved wavelength stability while maintaining a manageable number of layers through optimized parameter progression.
3Productivity
If multiple composition gradient layers are introduced, then threshold current density is reduced, but manufacturing process becomes more difficult
Solution Approach 1:
The patent optimizes epitaxial growth parameters by systematically varying In composition ratios (x1, x2, x3) across layers. This parameter change approach enables controlled reduction of threshold current density while maintaining manufacturability through established graded buffer and quantum well growth techniques.
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 reduces the laser oscillation threshold current density and inhibits short-wavelength shifts, enhancing the efficiency and stability of laser emission, particularly in the blue and green wavelength range.
Implementation Method 1
a first p-side composition gradient layer made of InxGa1-xN and having an In composition ratio x decreasing in a range of 0 to less than 1 upward in the first p-side composition gradient layer, a second p-side composition gradient layer disposed between the first p-side composition gradient layer and the electron barrier layer, made of AlyGa1-yN, and having an Al composition ratio y increasing in a range of more than 0 to less than 1 upward in the second p-side composition gradient layer
Data Source
AI summary
A semiconductor laser element includes an n-side semiconductor layer, an active layer and a p-side semiconductor layer. The p-side semiconductor layer includes, in order from the active layer, a first p-side composition gradient layer made of undoped InxGa1-xN and having an In composition ratio x decreasing in a range of 0 to less than 1 with distance from the active layer, an intermediate layer made of undoped AlzGa1-zN, and having an Al composition ratio z in a range of more than 0, a second p-side composition gradient layer made of undoped AlyGa1-yN, and having an Al composition ratio y increasing in a range of more than z to less than 1 with distance from the active layer, one or more p-type semiconductor layers containing a p-type impurity, and an electron barrier layer having a band gap energy larger than the second p-side composition gradient layer and containing a p-type impurity.