Diode Barrier Region Suppresses Hole Injection
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Solution Overview
Problem
Existing diodes face challenges in reducing switching loss due to incomplete suppression of hole injection into the n− drift region from the p anode region, leading to significant switching losses despite previous techniques.
Innovation Solution
The diode design incorporates a barrier region with higher impurity concentration than the drift region, connected to the anode electrode through a Schottky junction, which suppresses hole injection and includes a pillar region with even higher impurity concentration than the barrier region to further reduce switching losses, along with an electric field progress preventing region and trench structures to enhance voltage resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a p anode region is used in a conventional PN diode, then forward conduction is achieved, but hole injection into the n− drift region occurs causing significant switching loss
Solution Approach 1:
An n-type barrier region is introduced as an intermediary layer between the p-type anode region and the n− drift region. This barrier region acts as a mediator that blocks hole injection into the drift region while maintaining forward conduction through the pn junction. The barrier region with higher impurity concentration creates a potential barrier that prevents holes from reaching the drift region, thereby reducing switching loss without affecting the diode's forward conduction capability.
Solution Approach 2:
The barrier region is created with locally different impurity concentration (higher n-type doping) compared to the surrounding drift region. This local quality change creates a potential barrier specifically at the anode-drift region interface, allowing the structure to suppress hole injection only in the critical region where it occurs, while maintaining the overall diode functionality. The localized modification targets the specific problem area without altering the entire device structure.
2Loss of energy
If the p anode region size is reduced to reach-through limit to suppress hole injection, then switching loss is reduced, but reverse recovery characteristics are not sufficiently improved
Solution Approach 1:
The n-type barrier region serves as an intermediary that provides dual functionality: it suppresses hole injection during forward conduction (reducing switching loss) and restricts reverse current during reverse bias (improving reverse recovery characteristics). By positioning this barrier region between the anode and drift region, it acts as a gate that controls carrier flow in both forward and reverse directions, simultaneously addressing both performance parameters.
3Loss of energy
If a barrier region with higher impurity concentration is introduced, then hole injection is suppressed, but device complexity increases
Solution Approach 1:
The barrier region is created by changing the impurity concentration parameter in the semiconductor structure. By introducing a region with higher n-type doping concentration between the anode and drift region, the electrical properties are modified to create a potential barrier. This parameter change approach allows suppression of hole injection through a simple doping profile modification rather than adding complex structural elements, maintaining manufacturing simplicity while achieving the desired effect.
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 configuration significantly reduces switching loss and reverse recovery time while maintaining voltage resistance, without the need for lifetime control of the drift region, and improves voltage resistance to reverse bias.
Implementation Method 1
a pillar region formed so as to connect the barrier region to the anode electrode and made of a first conductivity type semiconductor having a concentration higher than that of the barrier region. In the diode, the pillar region and the anode electrode are connected through a Schottky junction.
Implementation Method 2
injection of holes into the drift region from the anode region is suppressed. Since the voltage drop at the Schottky interface is sufficiently smaller than a built-in voltage of a pn junction between the anode region and the barrier region
Implementation Method 3
an electric field is distributed to not only a depletion layer growing from the Schottky interface between the pillar region and the anode electrode but also a depletion layer growing from the interface of the pn junction between the anode region and the barrier region. Thereby, an electric field applied to the Schottky interface between the pillar region and the anode electrode is reduced.
Data Source
AI summary
Disclosed is a technique capable of reducing loss at the time of switching in a diode. A diode disclosed in the present specification includes a cathode electrode, a cathode region made of a first conductivity type semiconductor, a drift region made of a low concentration first conductivity type semiconductor, an anode region made of a second conductivity type semiconductor, an anode electrode made of metal, a barrier region formed between the drift region and the anode region and made of a first conductivity type semiconductor having a concentration higher than that of the drift region, and a pillar region formed so as to connect the barrier region to the anode electrode and made of a first conductivity type semiconductor having a concentration higher than that of the barrier region. The pillar region and the anode are connected through a Schottky junction.