Schottky Barrier Diode Low Forward Voltage and Leak Current Trade-off
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Schottky barrier diodes face a trade-off between low forward voltage and low leak current characteristics, with increased forward voltage leading to reduced leak current and vice versa, and the depletion layer pinch-off method is difficult to implement effectively, especially in diodes with low resistivity epitaxial layers, resulting in inadequate leak current suppression and increased switching time.
Innovation Solution
A semiconductor device with a semiconductor substrate of a first general conductivity type and impurity regions of a second general conductivity type, featuring a patterned metal layer forming a Schottky junction away from impurity regions and another metal layer forming a Schottky junction with exposed substrate areas, utilizing metal layers with distinct work function differences to control current paths under forward and reverse biases, ensuring low forward voltage and low leak current characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the work function difference φ Bn between the N− type epitaxial layer and the Schottky metal layer is increased, then the leak current at reverse voltage is reduced, but the forward voltage is increased
Solution Approach 1:
The patent divides the Schottky barrier diode structure into multiple regions with different metal layers. A first metal layer with a larger work function difference is used in regions where leak current suppression is critical, while a second metal layer with a smaller work function difference is used in regions where low forward voltage is prioritized. This spatial segmentation allows simultaneous optimization of both leak current and forward voltage characteristics across different parts of the device.
Solution Approach 2:
The patent applies different metal materials with distinct work function characteristics to different locations on the N− type epitaxial layer. By selecting metal layers with appropriate work function differences for specific regions, the device achieves locally optimized performance - high leak current suppression in some areas and low forward voltage in others - thereby resolving the overall trade-off.
2Object-generated harmful factors
If the depletion layer pinch-off method is used to suppress leak current, then the leak current characteristics improve, but the switching time increases and the method is difficult to implement effectively in diodes with low resistivity epitaxial layers
Solution Approach 1:
The patent segments the current conduction paths by using multiple metal layers with different work function characteristics. During reverse bias, the first metal layer region with larger work function difference dominates to suppress leak current. During forward bias, the second metal layer region with smaller work function difference provides low-resistance current paths. This segmentation eliminates the need for depletion layer pinch-off, thereby reducing switching time while maintaining leak current suppression.
Solution Approach 2:
The patent creates dynamically switchable current paths that adapt to bias conditions. The different metal layers are strategically positioned and designed with appropriate work function differences so that under reverse bias the high-barrier regions suppress leak current, while under forward bias the low-barrier regions enable fast carrier injection. This dynamic behavior allows the device to optimize performance for each operating mode without the delays associated with depletion layer formation and collapse.
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
The solution enables the Schottky barrier diode to operate with both low forward voltage and low leak current characteristics by selectively forming current paths using metal layers with different work function differences, effectively managing depletion layers to achieve improved performance across bias conditions.
Implementation Method 1
a Schottky metal layer 25 is provided, which forms a Schottky junction with a surface thereof
Implementation Method 2
A factor in determining characteristics of the Schottky barrier diode 110 is a work function difference φ Bn between the N− type epitaxial layer 21b and the Schottky metal layer 25
Implementation Method 3
When a reverse bias is applied to the Schottky barrier diode 120, as shown in FIG. 7B, a depletion layer 40 is spread into the N− type epitaxial layer 31b from the P+ type regions 33
Data Source
AI summary
Since VF and IR characteristics of a Schottky barrier diode are in a trade-off relationship, there has heretofore been a problem that an increase in a leak current is unavoidable in order to realize a low VF. Moreover, there has been a known structure which suppresses the leak current in such a manner that a depletion layer is spread by providing P+ regions and a pinch-off effect is utilized. However, in reality, it is difficult to completely pinch off the depletion layer. P+ type regions are provided, and a low VF Schottky metal layer is allowed to come into contact with the P+ type regions and depletion regions therearound. A low IR Schottky metal layer is allowed to come into contact with a surface of a N type substrate between the depletion regions. When a forward bias is applied, a current flows through the metal layer of low VF characteristic. When a reverse bias is applied, a current path narrowed by the depletion regions is formed only in the metal layer portion of low IR characteristic. Thus, a low VF and low IR Schottky barrier diode can be realized.