Surface-Emitting Laser Electrode Stack for Solder Diffusion Control
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Solution Overview
Problem
Surface light-emitting type light-emitting elements with a photonic crystal layer experience a decrease in light output over time due to heat-induced diffusion of solder materials, leading to uneven surfaces and reduced light reflectance.
Innovation Solution
A light-emitting element with a substrate and semiconductor laminate body structure, featuring a metal electrode film with a multilayer configuration that includes an adhesion layer, a highly reflective layer, a barrier layer, and a bonding layer, where the barrier layer has a lower diffusion degree to prevent solder material diffusion and maintain light reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a metal electrode film with a simple laminate structure (lower layer for ohmic contact and upper layer for solder contact) is used, then the device complexity is low and ease of manufacture is high, but light output decreases with time and light output efficiency is low due to solder material diffusion
Solution Approach 1:
The metal electrode film is segmented into multiple functional layers: a lower layer for ohmic contact, an intermediate layer with moderate diffusion degree, and an upper layer for solder contact. This segmentation allows each layer to perform its specific function while preventing harmful interactions between the lower and upper layers, thereby maintaining light output stability without significantly complicating the manufacturing process.
Solution Approach 2:
An intermediate layer is introduced between the lower layer and the upper layer to act as a mediator. This intermediate layer has a diffusion degree that is lower than the upper layer but higher than the lower layer, serving as a buffer that prevents solder material from diffusing into the lower layer while still allowing controlled interaction. This mediator layer resolves the contradiction by maintaining reliability without excessive manufacturing complexity.
2Reliability
If a multilayer metal electrode film structure is used to prevent solder material diffusion, then light output stability is improved, but the device complexity increases
Solution Approach 1:
Different layers of the metal electrode film are assigned different local qualities in terms of diffusion degree. The lower layer has low diffusion degree for stable ohmic contact, the intermediate layer has moderate diffusion degree for controlled interaction, and the upper layer has higher diffusion degree for solder bonding. This local differentiation of properties allows the system to achieve high reliability while keeping the overall structure manageable and not excessively complex.
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
The solution effectively suppresses the chronological decrease in light output by preventing solder material diffusion and maintaining light reflectance, ensuring high light output efficiency over time.
Implementation Method 1
a layer (for example, a photonic crystal layer) forming a resonance mode in a direction along the main surface of the substrate
Implementation Method 2
The resonance-mode forming layer includes a basic layer and a plurality of modified refractive index regions that each have a refractive index different from that of the basic layer
Implementation Method 3
The remaining part of the light outputted from the layer forming the resonance mode travels toward the other surface of the light-emitting element and is reflected by a metal electrode film provided on the other surface
Implementation Method 4
a third layer provided between the second layer and the second layer surface, and having a lower diffusion degree than the second layer with respect to a diffusion degree of a solder material
Data Source
AI summary
One aspect relates to a light-emitting element having a layer forming a resonance mode. The light-emitting element includes a structure body constituted by a substrate and a semiconductor laminate body including a first cladding layer, a second cladding layer, an active layer, and a resonance-mode forming layer including a basic layer and modified refractive index regions. A laser light output region and a metal electrode film are on opposing surfaces of the structure body. The metal electrode film includes a first layer forming ohmic contact with the structure body, a second layer reflecting light from the resonance-mode forming layer, a third layer, and a fourth layer for solder bonding. The third layer has a different composition from the second layer and the fourth layer, and has a lower diffusion degree than the second layer and the fourth layer to that of a solder material.