Ohmic Contact Paste for P-type Semiconductor Using Metal Oxide
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Solution Overview
Problem
Forming ohmic contacts to p-type semiconductor materials with high work functions, such as GaN and ZnO, is challenging due to the higher work function of these materials compared to available contact metals, requiring complex processes like high-temperature treatments or vacuum deposition methods, which are not suitable for flexible substrates like PET.
Innovation Solution
A paste comprising rhenium or molybdenum oxide with a binder, such as polyvinylalcohol, is applied to the substrate without a vacuum or thermal process, allowing for the formation of ohmic contacts through a simple process that minimizes heat exposure and can be used on flexible substrates like GaN.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional contact metals (Pt, Au) are used for p-type semiconductor contact, then the work function is relatively high, but ohmic contact cannot be formed due to Schottky barriers
Solution Approach 1:
The patent changes the material parameter from conventional metals to metal oxides (MoO2, ReO2) with higher work functions (higher than 6 eV). This parameter change enables the formation of ohmic contacts to p-type semiconductors by overcoming the Schottky barrier limitation that plagues conventional contact metals.
Solution Approach 2:
The patent uses composite material structures including metal oxide layers (MoO2, ReO2) combined with doping treatments. This composite approach combines the high work function advantage of metal oxides with the electrical conductivity enhancement from doping, achieving both high work function and low contact resistance.
2Reliability
If metal oxide (MoO2, ReO2) is used through vacuum process, then ohmic contact can be formed, but the contact is weak and heat treatment of 200° C. or above is needed
Solution Approach 1:
The patent applies preliminary doping treatment to the p-type semiconductor before forming the metal oxide contact. This preliminary action modifies the semiconductor properties in advance, enabling the formation of strong ohmic contacts at lower temperatures (around 100° C.) without requiring high-heat treatment that would weaken the contact.
3Reliability
If high temperature process is used for Al contact to p-type Si, then ohmic contact can be formed, but the process complexity increases due to high temperature requirements
Solution Approach 1:
The patent changes the contact material from Al to metal oxides (MoO2, ReO2) with inherently higher work functions. This parameter change eliminates the need for high-temperature processing (above 577° C. for Al-Si contacts), simplifying the manufacturing process while maintaining ohmic contact quality.
4Reliability
If vacuum deposition method is used for Mo or Re metal deposition, then metal oxide layer can be formed, but the process complexity increases and cannot be applied to PET or PI substrates
Solution Approach 1:
The patent replaces the mechanical vacuum deposition system with a chemical solution-based approach. Instead of using vacuum deposition equipment to deposit Mo or Re metals followed by oxidation, the patent directly applies metal oxide solutions or precursors that can be deposited on flexible substrates like PET and PI without requiring vacuum environments.
Solution Approach 2:
The patent changes the deposition method from physical vapor deposition (vacuum process) to chemical solution processing. This parameter change in the deposition technique enables compatibility with flexible substrates (PET, PI) that cannot withstand vacuum deposition conditions, while still forming high-quality metal oxide contact layers.
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 enables the formation of reliable ohmic contacts with reduced electrical resistance and specific contact resistance, suitable for applications in organic solar cells and flexible devices, using non-vacuum and non-thermal processes, overcoming the limitations of high work function p-type semiconductor materials.
Implementation Method 1
a paste for ohmic contact to p-type semiconductor, including a metal oxide and a binder... applying the paste to a substrate, drying the substrate
Data Source
AI summary
The present disclosure relates to a paste for ohmic contact to p-type semiconductor, including a metal oxide and a binder, wherein the metal oxide is a rhenium oxide or a molybdenum oxide.