Carbon-Doped GaN Photoconductive Switch for High-Voltage Low Resistance
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Solution Overview
Problem
Conventional light controlled semiconductor switches, particularly those made from silicon carbide, suffer from high resistance and low minority carrier lifetime, limiting their effectiveness in power switching applications due to indirect bandgap and sub bandgap illumination.
Innovation Solution
A vertical and lateral light controlled semiconductor switch (LCSS) using gallium nitride (GaN) doped with carbon, which switches from a non-conductive off-state to a conductive on-state when excited by light, achieving low resistance and high voltage blocking through photo-generation of carriers in the conduction band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional semiconductor switches (MOSFETs) are used to achieve high voltage blocking capability, then breakdown voltage is improved, but on-state resistance increases
Solution Approach 1:
The patent replaces electrical gate control with optical control using a light-controlled semiconductor switch. The switch is activated by light photons rather than electrical signals, eliminating the need for high-voltage gate drivers and reducing electrical noise while maintaining high voltage blocking capability and low on-state resistance through direct optical excitation of carriers in the photoactive layer
Solution Approach 2:
The patent changes the control mechanism from electrical voltage parameters to optical parameters (light wavelength, intensity, and pulse duration). By using sub-bandgap light illumination, the switch achieves low on-state resistance without requiring high gate voltages, thereby resolving the tradeoff between breakdown voltage and on-state resistance
2Ease of operation
If electrical gate drivers are used to control semiconductor switches, then switching capability is improved, but noise issues increase
Solution Approach 1:
The patent substitutes electrical gate driver control with optical control using light sources. The light-controlled switch responds to optical signals rather than electrical voltages, eliminating electromagnetic interference and noise from gate drivers while preserving full switching capability through direct photogeneration of charge carriers in the semiconductor photoactive layer
3Stress or pressure
If vanadium doping is used in silicon carbide to create semi-insulating material, then insulation capability is improved, but photoresponsivity decreases
Solution Approach 1:
The patent changes the doping approach by using carbon doping in GaN instead of vanadium doping in SiC. Carbon doping creates deep-level traps that provide semi-insulating properties while maintaining high photoresponsivity under sub-bandgap illumination, as the carbon-related defect states can be optically activated to generate carriers without requiring high-energy photons
Solution Approach 2:
The patent employs a composite structure combining GaN photoactive layer with carbon doping to achieve both semi-insulating properties and high photoresponsivity. The carbon-doped GaN layer integrates insulating capability through deep-level traps while maintaining optical sensitivity, resolving the contradiction between insulation and photoresponsivity present in vanadium-doped SiC
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 GaN:C LCSS offers low resistance in the on-state and high resistance in the off-state, with improved switching times and reduced gate driver noise, suitable for high-voltage operations and RF generation applications.
Implementation Method 1
when the light energy impinging on the semiconductor body is sufficient to excite electrons into the conduction band of the semiconductor body photoactive layer
Implementation Method 2
Light controlled semiconductor switches (LCSS) are opto-electrical devices made of semiconductor material that conduct electricity when they are turned on with light through optical excitation
Data Source
AI summary
A light controlled semiconductor switch (LCSS), method of making, and method of using are provided. In embodiments, a vertical LCSS includes: a semiconductor body including a photoactive layer of gallium nitride (GaN) doped with carbon; a first electrode in contact with a first surface of the semiconductor body, the first electrode defining an area through which light energy from at least one light source can impinge on the first surface; and a second electrode in contact with a second surface of the semiconductor body opposed to the first surface, wherein the vertical LCSS is configured to switch from a non-conductive off-state to a conductive on-state when the light energy impinging on the semiconductor body is sufficient to raise electrons within the photoactive layer into a conduction band of the photoactive layer.