Optical Semiconductor Device With High-Resistance Burial Layer
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Solution Overview
Problem
Current semiconductor lasers face challenges such as high threshold current, low relaxation oscillation frequency, poor high-temperature characteristics, and parasitic capacitance, which limit their speed and reliability, especially in optical communication systems requiring high-speed and low power consumption.
Innovation Solution
The development of an optical semiconductor device with an InP substrate, featuring a first clad layer, Al-based semiconductor multi-layer films, and a burial semiconductor layer that is self-aligned to minimize lateral diffusion and parasitic capacitance, resulting in a reduced threshold current and increased relaxation oscillation frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a ridge type laser structure is used, then high speed operation can be achieved, but threshold current increases due to current diffusion
Solution Approach 1:
The patent extracts the harmful current diffusion effect by removing the air ridge structure that causes lateral current spread. Instead, it uses a planar waveguide structure with embedded high-resistance layers that confine current vertically without the lateral diffusion problem inherent in ridge structures, thereby reducing threshold current while maintaining high-speed capability
Solution Approach 2:
The patent introduces high-resistance semiconductor layers as intermediary elements between the n-type and p-type cladding layers. These intermediary layers act as current blocking barriers that prevent lateral current diffusion while allowing vertical current flow, thus resolving the contradiction between maintaining current confinement for high speed and preventing current leakage that increases threshold current
2Use of energy by moving object
If the active layer width is increased to reduce threshold current, then threshold current decreases, but relaxation oscillation frequency decreases
Solution Approach 1:
The patent applies local quality by creating a vertically stratified structure where different layers have different resistance properties. The high-resistance layers are strategically positioned to block lateral current diffusion locally, while the overall active region maintains optimal width for both low threshold current and high relaxation oscillation frequency. This localized control of current flow paths allows independent optimization of both parameters
3Ease of manufacture
If conventional laser structures are used, then manufacturing is simple, but parasitic capacitance increases reducing high-speed performance
Solution Approach 1:
The patent segments the cladding structure into multiple distinct layers with different resistance properties (n-type cladding, high-resistance blocking layers, p-type cladding). This segmentation allows each layer to perform its specific function - the high-resistance layers block parasitic current paths and reduce capacitance, while the conductive cladding layers provide necessary electrical connections, achieving high-speed performance without excessive manufacturing 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 configuration achieves a low threshold current, high relaxation oscillation frequency, and improved high-temperature stability, enabling stable and efficient high-speed operation with reduced power consumption, thus enhancing the reliability and performance of semiconductor lasers for optical communication.
Implementation Method 1
Al-based semiconductor multi-layer films which are disposed on the lower layer side of the first conductivity type semiconductor layer, are formed by overlapping a plurality of semiconductor layers including an Al element, and have a quantum well active layer
Implementation Method 2
at least one burial semiconductor layer that comes into contact with two opposite common side walls formed by the first conductivity type semiconductor layer and the Al-based semiconductor multi-layer films
Data Source
AI summary
In a BH laser which uses InGaAlAs-MQW in an active layer, Al-based semiconductor multi-layer films including an InP buffer layer and an InGaAlAs-MQW layer, and an InGaAsP etching stop layer are formed in a mesa shape, and a p type InP burial layer is buried in side walls of the mesa shape. An air ridge mesa-stripe of a lateral center that is substantially the same as that of the mesa shape is formed on the mesa shape. According to the present structure, a leakage current can be considerably reduced, the light confinement coefficient can be made to be larger than in a BH laser in the related art, and thereby it is possible to implement a semiconductor laser with a low leakage current and a high relaxation oscillation frequency.