InGaAs Contact Layer in Infrared LEDs to Prevent Metal Diffusion
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Solution Overview
Problem
Semiconductor light-emitting devices with a center emission wavelength of 1000 to 2200 nm face challenges in reducing thickness and maintaining reliability, particularly experiencing time degradation in light output power and forward voltage due to the fragility of InP substrates and conventional semiconductor layer configurations.
Innovation Solution
A bonding-type semiconductor light-emitting device is developed using an n-type InGaAs contact layer instead of InGaAsP, with a specific In composition ratio and a conductive support substrate, allowing for improved lattice matching and reduced substrate thickness, and featuring a semiconductor laminate with a p-type cladding layer, active layers, and an n-type cladding layer, along with a reflective metal layer and n-side electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If an InP substrate is used as a support substrate, then the device can transmit infrared light effectively, but the device thickness cannot be reduced because the substrate accounts for the majority of the total thickness
Solution Approach 1:
The device is divided into two functional parts: the InP growth substrate is used only for epitaxial growth and then removed, while a separate conductive support substrate provides mechanical support. This segmentation allows the thin semiconductor laminate to be supported without requiring a thick InP substrate, reducing overall device thickness while maintaining structural integrity.
Solution Approach 2:
The InP substrate is extracted from its traditional role as a permanent support substrate. It is used temporarily during manufacturing for growing the semiconductor laminate, then removed through chemical etching. This extraction eliminates the thickness constraint imposed by the InP substrate while preserving its utility during the growth process.
2Volume of moving object
If the InP substrate is thinned to reduce device thickness, then the device becomes more compact, but the substrate breaks due to excessive thinning
Solution Approach 1:
A conductive support substrate acts as an intermediary between the thin semiconductor laminate and the final device structure. This intermediary provides the mechanical strength and thickness needed for device handling and operation, while allowing the semiconductor laminate itself to remain thin for reduced overall device thickness.
3Reliability
If an InGaAsP-based III-V semiconductor layer is used for the n-type semiconductor layer, then lattice matching with the InP substrate is achieved, but metal diffusion occurs degrading device performance over time
Solution Approach 1:
The InGaAsP-based n-type semiconductor layer is used as a temporary structure during manufacturing that serves its lattice-matching function but is then completely removed. This disposable layer enables the formation of reliable ohmic contacts without the long-term harmful effects of metal diffusion, as it does not remain in the final device structure.
Solution Approach 2:
The material composition of the n-type semiconductor layer is changed from InGaAsP-based to InGaAs-based. This parameter change eliminates P from the layer composition, preventing metal diffusion while maintaining the necessary electrical properties for ohmic contact formation. The InGaAs layer provides the required n-type conductivity without the lattice-matching benefits of InGaAsP, but this is compensated by the underlying InP cladding layer.
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 results in a semiconductor light-emitting device with enhanced reliability and reduced time deviations in light output power and forward voltage, achieving stable performance over time by using an n-type InGaAs contact layer that prevents metal diffusion and maintains ohmic contact.
Implementation Method 1
an n-type InGaAs contact layer that prevents metal diffusion and maintains ohmic contact
Implementation Method 2
a metal layer comprising a reflective metal provided on the conductive support substrate
Data Source
AI summary
A semiconductor light-emitting device includes: a conductive support substrate; a metal layer comprising a reflective metal provided on the conductive support substrate; a semiconductor laminate provided on the metal layer, the semiconductor laminate being a stack of a plurality of InGaAsP-based III-V group compound semiconductor layers containing at least In and P; an n-type InGaAs contact layer provided on the semiconductor laminate; and an n-side electrode provided on the n-type InGaAs contact layer. A center emission wavelength of light emitted from the semiconductor laminate is 1000 to 2200 nm.