Semiconductor Light Emitting Device Strain Buffer Layer
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Solution Overview
Problem
Semiconductor lasers with highly strained quantum well layers experience reduced operating life due to compressive strain, leading to fragility and reliability issues, especially when the strain exceeds 1%, necessitating improved crystal quality and durability.
Innovation Solution
Incorporating a strain buffer layer with compressive strain not exceeding the active layer's strain, adjacent to the active layer, to reduce lattice constant misfits and prevent crystal defect spread, thereby enhancing crystal quality and device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a highly strained quantum well layer with compressive strain not less than 1% is used in the active layer, then the optical power output is improved, but the operating life and reliability are significantly reduced due to crystal fragility
Solution Approach 1:
A strain buffer layer is introduced as an intermediary between the active layer and the clad layer. This buffer layer has a compressive strain amount that is less than the active layer's strain, acting as a transition zone that reduces the strain mismatch and prevents crystal defect propagation while allowing the active layer to maintain its high strain for optimal optical power output
Solution Approach 2:
The compressive strain amount is varied across different layers: the active layer maintains high compressive strain (≥1%) for optimal light emission, while the strain buffer layer has a reduced compressive strain amount (less than the active layer) to reduce mechanical stress and prevent crystal fragility, thus resolving the contradiction between power output and reliability
2Power
If the compressive strain amount in the active layer exceeds 1%, then the light emission performance is enhanced, but the crystal quality of adjacent layers deteriorates and reliability is significantly reduced
Solution Approach 1:
The strain buffer layer serves as a mediator that allows the active layer to achieve high compressive strain for improved light emission while preventing this high strain from degrading the crystal quality of adjacent clad layers. The buffer layer's intermediate strain value creates a gradual transition that protects crystal quality
Solution Approach 2:
Different layers are assigned different strain characteristics tailored to their specific functions: the active layer has high compressive strain optimized for light emission performance, while the strain buffer layer has reduced compressive strain optimized for maintaining crystal quality and preventing defect propagation in adjacent layers
Data Source
AI summary
In a semiconductor light emitting device having a conductive semiconductor substrate on which at least the following layers are stacked in the order listed below: a first clad layer; an active layer which includes at least one highly strained quantum well layer having a compressive strain amount of not less than 1% with respect to the conductive semiconductor substrate; and a second clad layer, a strain buffer layer adjacently formed on the active layer and includes a layer having a compressive strain amount not greater than the strain amount of the active layer is further provided.