Nitride Semiconductor Laser Diode High-Temperature Life
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Solution Overview
Problem
Nitride semiconductor laser diodes with InGaN light emitting layers face challenges in achieving long life characteristics, especially at high temperatures, due to increased dislocation density and lattice mismatch, which affects emission wavelength and efficiency.
Innovation Solution
Controlling the concentration of p-type impurity in a predetermined range near the InGaN light emitting layer, allowing dislocations to form while ensuring efficient hole supply, thereby improving life characteristics and maintaining crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the In content in the InGaN light emitting layer is increased to achieve longer emission wavelength (500 nm or greater), then the emission wavelength is extended to green region, but the dislocation density increases and life characteristics deteriorate sharply
Solution Approach 1:
The patent changes the chemical composition parameters of the light emitting layer by introducing P elements to form InGaNP alloy, which modifies the band gap structure and allows achieving 500 nm or greater emission wavelength without proportionally increasing In content, thereby reducing dislocation density and improving life characteristics
Solution Approach 2:
The patent uses composite material InGaNP (combining In, Ga, N, and P elements) instead of simple InGaN alloy, leveraging the unique properties of P elements to achieve desired emission wavelength while maintaining crystal quality and reducing harmful dislocations
2Temperature
If the In content in the InGaN light emitting layer is increased to achieve longer emission wavelength, then the emission wavelength is extended, but the lattice mismatch with GaN underlayer increases causing dislocation generation
Solution Approach 1:
The patent modifies the compositional parameters by incorporating P elements into the InGaN structure to form InGaNP, which changes the lattice constants and band gap energy, enabling wavelength tuning without proportional increase in lattice mismatch
Solution Approach 2:
The P elements act as an intermediary component that mediates between the In content requirement for long wavelength and the lattice mismatch problem, providing a compositional buffer that allows wavelength extension while maintaining structural compatibility with GaN substrate
3Device complexity
If conventional InGaN light emitting layer is used to achieve green emission, then the structure is simple, but the operating life at high temperature is only several tens of hours
Solution Approach 1:
The patent employs InGaNP composite material in the light emitting layer, which provides superior thermal stability and dislocation resistance compared to conventional InGaN, extending operating life to several thousand hours at high temperature while maintaining reasonable structural complexity
Solution Approach 2:
The patent optimizes compositional parameters (P content, In content ratios) in the InGaNP light emitting layer to achieve the right balance between emission wavelength, crystal quality, and thermal stability, enabling long operating life without excessive structural complexity
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 approach significantly extends the operating life of nitride semiconductor laser diodes at high temperatures, achieving several thousand hours of operation while maintaining high light emitting efficiency.
Implementation Method 1
Controlling the concentration of p-type impurity in a predetermined range near the InGaN light emitting layer
Implementation Method 2
nitride semiconductor laser diode using a nitride semiconductor... active layer having a light emitting layer
Implementation Method 3
increased dislocation density and lattice mismatch, which affects emission wavelength and efficiency
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A nitride semiconductor laser diode includes a substrate, an n-side nitride semiconductor layer formed on the substrate, an active layer formed on the n-side nitride semiconductor layer and having a light emitting layer including InxAlyGa1-x-yN (0<x<1, 0≤y<1, 0<x+y<1), and a p-side nitride semiconductor layer formed on the active layer. In the nitride semiconductor laser diode, the lasing wavelength of the nitride semiconductor laser diode is 500 nm or greater, dislocations originated in the active layer penetrate through the p-side nitride semiconductor layer, with the dislocation density in the p-side nitride semiconductor layer being 1×106 cm-2 or greater, and the concentration distribution of p-type impuritys in the depth direction is such that, from the light emitting layer toward the surface of the p-side nitride semiconductor layer, the concentration of the p-type impurity reaches a maximum value of 5×1018 cm-3 or greater within a range of 300 nm from the top portion of the light emitting layer which is closest to the p-side nitride semiconductor layer, and after reaching the maximum value, the concentration remains at 6×1017 cm-3 or greater in the above-described range of 300 nm.