High-k Dielectric Heterojunction for Reverse Breakdown Voltage
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Solution Overview
Problem
Wide band gap materials face challenges in achieving high breakdown fields across the rectifying junction due to limited bipolar doping and low Schottky barrier heights, limiting their potential for vertical power switching and rectification.
Innovation Solution
A device comprising a high-k dielectric material layer with a dielectric constant at least twice that of a semiconductor drift layer, combined with a metal Schottky contact and ohmic contact, which maintains a barrier to electron or hole tunneling at higher voltages and supports efficient carrier transport under bias conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Schottky junction is used to provide rectification, then excellent rectification performance is achieved, but the reverse breakdown voltage is limited by the Schottky barrier height which is significantly lower than the band gap
Solution Approach 1:
The patent combines a high-k dielectric material layer with a semiconductor drift layer to form a composite heterojunction structure. This composite structure maintains the rectification capability of Schottky junctions while the high-k dielectric layer with dielectric constant at least twice that of the semiconductor layer enables the structure to sustain much higher reverse breakdown voltages by reducing the electric field in the semiconductor layer under reverse bias.
2Power
If wide band gap materials are used for vertical power switching, then the Baliga Figure of Merit is significantly higher due to high breakdown fields and good transport properties, but bipolar doping is not available or presents technological challenges
Solution Approach 1:
The patent extracts the high-k dielectric material layer from the conventional single-layer semiconductor structure and places it in direct contact with the metal Schottky contact. This extraction allows the device to achieve high breakdown fields and good transport properties without requiring bipolar doping in the wide band gap semiconductor, thereby maintaining ease of manufacture while achieving high Power.
3Strength
If the entire band gap is presented across the rectifying junction, then the predicted breakdown field is achieved, but this is challenging in wide band gap materials where bipolar doping is not available
Solution Approach 1:
The patent introduces a high-k dielectric material layer as an intermediary between the metal Schottky contact and the semiconductor drift layer. This intermediary layer has a dielectric constant at least twice that of the semiconductor layer, which allows the structure to achieve the predicted breakdown field by redistributing the electric field, with the high-k layer bearing a significant portion of the voltage stress while maintaining ease of manufacture through avoidance of complex doping processes.
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 device achieves a low electric field in the semiconductor layer under reverse bias and efficient carrier transport under forward bias, maintaining a barrier to tunneling at higher voltages than conventional metal/semiconductor junctions, enhancing rectification and transport properties.
Implementation Method 1
Under a reverse bias, the dielectric constant discontinuity leads to a very low electric field in the second layer
Implementation Method 2
Schottky junctions can provide excellent rectification but the reverse breakdown of Schottky rectifiers is limited by the Schottky barrier height
Implementation Method 3
Under a forward bias, electrons flow through the first layer, into the metal ohmic contact
Data Source
AI summary
A device is provided that comprises a first layer deposited onto a second layer. The second layer comprises a lightly doped n-type or p-type semiconductor drift layer, and the first layer comprises a high-k material with a dielectric constant that is at least two times higher than the value of the second layer. A metal Schottky contact is formed on the first layer and a metal ohmic contact is formed on the second layer. Under reverse bias, the dielectric constant discontinuity leads to a very low electric field in the second layer, while the electron barrier created by the first layer stays almost flat. Under forward bias, electrons flow through the first layer, into the metal ohmic contact. For small values of conduction band offset or valence band offset between the first layer and the second layer, the device is expected to support efficient electron or hole transport.