N-Type Germanium Wafers With Phosphorus Doping and Low Resistivity
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Solution Overview
Problem
Existing methods for producing n-type doped germanium wafers with low resistivity and dislocation-free crystals are inefficient and introduce contaminants or fail to achieve the desired low resistivity and dislocation-free state, which are crucial for enhancing the performance of opto-electronic devices like VCSELs and plasmonic sensors.
Innovation Solution
The use of phosphorus as a single dopant in the Czochralski process to grow n-type doped germanium monocrystals, ensuring a high n-type doping level of at least 1×10^18/cm^3, combined with precise control to achieve dislocation-free crystals with resistivity below 10 mOhm·cm, using GeP as the dopant source to minimize impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If calcium orthophosphate is used as dopant source to achieve heavy phosphorus doping, then resistivity can be reduced below 2 mOhm·cm, but dislocations are necessarily introduced into the crystal
Solution Approach 1:
The patent uses a dopant chamber as an intermediary device to deliver phosphorus to the melt. The chamber is positioned close to the melt surface and phosphorus is introduced via evaporation, allowing controlled doping without directly adding solid dopant sources that would cause dislocations. This intermediary approach enables precise dopant delivery while maintaining crystal integrity.
Solution Approach 2:
The patent changes the physical state and delivery method of phosphorus from solid calcium orthophosphate to gaseous phosphorus vapor. By controlling temperature parameters to evaporate phosphorus from the dopant chamber and deliver it to the melt, the process achieves heavy doping without the mechanical stress and contamination that cause dislocations in traditional solid-source doping methods.
2Manufacturing precision
If multiple electrically active dopants are simultaneously added to achieve very low resistivity, then resistivity can be reduced below 2 mOhm·cm, but the process complexity increases and contaminants may be introduced
Solution Approach 1:
The patent extracts the essential function of heavy doping from complex multi-dopant systems and achieves it through a single dopant (phosphorus) delivered via an evaporation chamber. This simplifies the doping process by removing the need to manage multiple dopant sources, their interactions, and associated contaminants, while still achieving the target resistivity through controlled phosphorus delivery.
3Manufacturing precision
If dopant chamber is used to introduce phosphorus via evaporation, then high doping levels can be achieved, but additional equipment and temperature control requirements increase process complexity
Solution Approach 1:
The dopant chamber serves multiple functions: it acts as a reservoir for phosphorus, a heating zone for evaporation, a delivery system via vapor transport, and a control mechanism for doping rate. This multi-functionality consolidates what would otherwise require separate systems into a single integrated component, reducing overall process complexity despite the added capabilities.
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 method allows for the production of dislocation-free n-type doped germanium wafers with controlled resistivity, enhancing the performance of opto-electronic devices by ensuring high electron density and minimizing plasmonic losses.
Implementation Method 1
When the temperature is raised to the melting point of phosphorus, the phosphorus is released as a gas
Implementation Method 2
The present invention provides a process for the manufacture of dislocation-free monocrystalline Ge
Data Source
AI summary
The invention concerns monocrystalline dislocation-free Ge, n-type doped, and having a resistivity of less than 10 mOhm·cm, characterized in that phosphorus is the single dopant. Such crystals can be obtained by using the Czochralski pulling technique with GeP as dopant.