InP Window Layer Growth Temperature Control for Photodiode Arrays
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Solution Overview
Problem
The existing manufacturing methods for photodiode arrays using InGaAs/GaAsSb type-II semiconductors face challenges in maintaining the crystalline quality of the absorption layer and reducing surface defects, leading to defective pixels due to high growth temperatures required for the InP window layer, which degrades the absorption layer's quality and increases dark current.
Innovation Solution
A method involving metal-organic vapor phase epitaxy (MOVPE) is used to grow a window layer composed of a compound semiconductor including P, with a growth temperature lower than the absorption layer, using tertiarybutylphosphine as a raw material for P, to prevent degradation of the absorption layer's crystalline quality and reduce dark current, while forming a multiple quantum well structure with InGaAs and GaAsSb layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the InP window layer is grown at a high temperature (640°C or more) to reduce surface defects, then the surface defect density is reduced, but the crystalline quality of the absorption layer is degraded by heat
Solution Approach 1:
The patent changes the growth temperature parameter from conventional high temperature (640°C or more) to a lower temperature range (400-600°C) by using TBP as the phosphorus source instead of PH3, thereby reducing thermal damage to the absorption layer while still achieving low surface defect density through optimized growth conditions
Solution Approach 2:
The patent replaces the conventional PH3 source with TBP (tertiarybutylphosphine), which allows growth at lower temperatures. This substitution enables the window layer to be grown under milder conditions that preserve the absorption layer's crystalline quality while still producing the desired low defect density
2Stability of the object's composition
If the growth temperature of the window layer is reduced to maintain absorption layer quality, then the crystalline quality is maintained, but surface defects increase
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: growth temperature (400-600°C), phosphorus source (TBP), and growth pressure, to achieve the counterintuitive result of low surface defect density at lower temperatures, thereby maintaining both absorption layer quality and window layer surface quality
Solution Approach 2:
The patent employs monitoring and control of growth conditions to optimize the balance between temperature and surface quality, using feedback from defect analysis to refine growth parameters and achieve the desired outcome
3Ease of manufacture
If phosphine (PH3) is used as raw material for P in InP window layer growth, then the window layer can be grown, but the growth temperature must be set high (640°C), which degrades the absorption layer
Solution Approach 1:
The patent replaces PH3 with TBP (tertiarybutylphosphine) as the phosphorus source. This substitution enables window layer growth at lower temperatures (400-600°C) while maintaining manufacturing feasibility, thereby eliminating the need for high-temperature growth that degrades the absorption layer
Solution Approach 2:
The patent changes the chemical nature of the phosphorus source from PH3 to TBP, which fundamentally alters the growth temperature requirements and enables low-temperature window layer growth that preserves absorption layer quality
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 maintains excellent crystalline quality of the absorption layer, reduces surface defects, and decreases dark current, resulting in improved device characteristics and a lower percentage of defective pixels, enhancing the photodiode array's performance and yield.
Implementation Method 1
a window layer composed of a compound semiconductor including P is grown on the absorption layer
Implementation Method 2
A method involving metal-organic vapor phase epitaxy (MOVPE) is used to grow a window layer
Data Source
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AI summary
Provided are a photodiode array and its manufacturing method, which maintain the crystalline quality of an absorption layer formed on a group III-V semiconductor substrate to obtain excellent characteristics, and which improve the crystallinity at the surface of a window layer; an epitaxial wafer used for manufacturing the photodiode array; and a method for manufacturing the epitaxial wafer. A method for manufacturing a photodiode array 1 having a plurality of absorption regions 21, includes the steps of: growing an absorption layer 7 on an n-type InP substrate 3; growing an InP window layer on the absorption layer 7; and diffusing a p-type impurity in regions, in the window layer 11, corresponding to the plurality of absorption regions 21. The window layer 11 is grown by MOVPE using only metal-organic sources, at a growth temperature equal to or lower than that of the absorption layer 7.