Optical Semiconductor Mesa Structure Narrowing Hole Leak Path
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Solution Overview
Problem
Existing methods for manufacturing optical semiconductor devices face challenges in narrowing the hole leak path due to variations in temperature distribution and material decomposition rates, leading to increased threshold current and degraded direct modulation properties.
Innovation Solution
A method involving the formation of a mesa structure with a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer, where a first burying layer is grown on both sides of the mesa structure above the active layer, and a depressed face is etched on the upper face of the second conductivity type cladding layer, followed by the growth of a second burying layer on the depressed face and the first burying layer, effectively reducing the hole leak path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the thickness of the p-type cladding layer is reduced and the n-type InP burying layer is arranged closer to the p-type cladding layer, then the hole leak path is narrowed and threshold current is reduced, but the distance between the n-type InP burying layer and the p-type cladding layer cannot be kept constant due to temperature distribution and material decomposition rate differences
Solution Approach 1:
A mask is formed on the p-type cladding layer before growing the n-type InP burying layer. This preliminary masking action defines the precise position where the burying layer will grow, ensuring that the distance between the burying layer and the p-type cladding layer remains constant throughout the wafer face, compensating for temperature distribution and material decomposition rate variations.
Solution Approach 2:
The mask serves as an intermediary element that mediates between the p-type cladding layer and the n-type InP burying layer. By introducing this intermediate component, the patent achieves precise control over the spacing between the cladding layer and burying layer, eliminating the precision problems caused by direct growth without masking.
2Loss of energy
If a mask is formed on the p-type cladding layer to grow the burying layer selectively, then the hole leak path can be controlled, but the mask causes distortion of the active layer when the thickness of the p-type cladding layer is reduced
Solution Approach 1:
The patent applies local quality by forming the mask only in specific regions where selective burying layer growth is needed, rather than uniformly across the entire structure. This localized masking approach allows hole leak path control at critical interfaces while minimizing mask-induced stress and distortion on the active layer in other regions.
3Loss of energy
If the thickness of the p-type cladding layer is reduced to narrow the hole leak path, then threshold current is reduced, but it becomes difficult to maintain constant distance between the n-type InP burying layer and the p-type cladding layer across the wafer face
Solution Approach 1:
The mask formation process provides a feedback mechanism that compensates for wafer-level variations. By using the mask as a reference structure formed before epitaxial growth, the system automatically compensates for temperature distribution and material decomposition rate differences across the wafer face, ensuring uniform spacing between the p-type cladding layer and n-type InP burying layer throughout the entire wafer.
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 reduces the threshold current and improves direct modulation properties by narrowing the hole leak path and maintaining consistent thickness, thereby minimizing variations and active layer distortion.
Implementation Method 1
growing a first burying layer burying both sides of the mesa structure at higher position than the active layer; growing a second burying layer of the first conductivity type on the depressed face of the second conductivity type cladding layer and the first burying layer
Data Source
AI summary
A method of manufacturing an optical semiconductor device including: forming a mesa structure including a first conductivity type cladding layer, an active layer and a second conductivity type cladding layer in this order on a first conductivity type semiconductor substrate, an upper most surface of the mesa structure being constituted of an upper face of the second conductivity type cladding layer; growing a first burying layer burying both sides of the mesa structure at higher position than the active layer; forming an depressed face by etching both edges of the upper face of the second conductivity type cladding layer; and growing a second burying layer of the first conductivity type on the depressed face of the second conductivity type cladding layer and the first burying layer.