Nitride Semiconductor Laser Barrier Layer COD Resistance
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Solution Overview
Problem
Nitride semiconductor laser elements face challenges in maintaining high catastrophic optical damage (COD) levels when operated at high power, leading to premature failure and reduced longevity.
Innovation Solution
A nitride semiconductor laser element structure is designed with a quantum well active layer comprising undoped InGaN well layers and barrier layers with specific In composition ratios, including a GaN second layer to enhance COD resistance, and undoped adjacent layers to reduce threshold current density and improve crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a quantum well active layer with doped barrier layer is used to reduce threshold current, then the threshold current is reduced, but the COD level deteriorates when operated at high power
Solution Approach 1:
The barrier layer is divided into three regions with different doping concentrations: a first region adjacent to the well layer with high doping concentration to facilitate carrier generation, a second region in the middle with intermediate doping concentration, and a third region away from the well layer with low doping concentration to suppress internal loss. This local quality differentiation resolves the contradiction by optimizing both threshold current and COD level in different spatial regions of the same barrier layer.
2Stability of the object's composition
If a buffer layer with high In composition ratio is used to alleviate lattice constant variation, then the lattice mismatch is reduced, but the device complexity increases
Solution Approach 1:
The barrier layer is segmented into three distinct regions with progressively varying doping concentrations rather than using a complex multi-layer buffer structure. This segmentation approach achieves lattice constant stabilization through the gradual composition change within the barrier layer itself, eliminating the need for additional buffer layers and reducing overall device complexity.
Data Source
AI summary
A nitride semiconductor laser element includes a lower clad layer, a lower adjacent layer, a quantum well active layer, an upper adjacent layer and an upper clad layer in this order. The quantum well active layer includes a plurality of well layers formed of undoped InGaN, and an undoped barrier layer sandwiched between the well layers. The barrier layer includes a first layer formed of InGaN, a second layer formed of GaN, and a third layer formed of InGaN. The In composition ratio of the first layer and the In composition ratio of the third layer are less than half the In composition ratio of the well layer.