GaN HEMT Switch Insulated Gate Reduces Current Drain
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Solution Overview
Problem
Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) used as switches require negative voltage to turn OFF, which is typically generated from a smaller positive supply voltage using multiple stages of charge pump circuits, leading to large capacitors and high current drain, resulting in power loss and heat generation, especially in high-power RF applications where parasitic components degrade signal quality.
Innovation Solution
A GaN HEMT switch with an insulated gate that reduces gate current, allowing for integration of capacitors on a CMOS controller without external components, using a multigate structure to handle higher voltages and reduce insertion loss, and biasing the gate at a higher negative voltage to prevent switch activation during RF voltage peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple stages of charge pump circuits are used to generate negative voltage, then the switch can be turned OFF, but the capacitor size increases and current drain increases
Solution Approach 1:
The patent changes the gate structure parameters by introducing an insulated gate layer between the gate electrode and the semiconductor layer, fundamentally altering how the gate controls the channel. This allows the switch to be driven by positive voltages only, eliminating the need for multiple charge pump stages and large capacitors while maintaining reliable OFF capability.
Solution Approach 2:
The patent replaces the complex mechanical/electrical system of multiple charge pump stages with a simplified field effect mechanism. The insulated gate creates an electric field that controls carrier flow through the semiconductor layer, enabling voltage generation without mechanical charge pumping circuits.
2Reliability
If multiple stages of charge pump circuits are used to generate negative voltage, then the switch can be turned OFF, but power loss and heat generation increase
Solution Approach 1:
The insulated gate structure changes the electrical parameters of the switch, allowing it to operate with positive voltages only. This eliminates the power loss associated with multiple charge pump stages, as the gate current is significantly reduced due to the insulating barrier, thereby reducing overall power consumption and heat generation.
3Ease of manufacture
If parasitic components are present in the switch, then the switch can be constructed, but signal quality degrades
Solution Approach 1:
The patent applies local quality by creating highly doped regions (source and drain) with specific carrier concentrations that are locally optimized for low resistance contacts. The insulated gate region is separately optimized for low parasitic capacitance. This localized optimization of different regions reduces overall parasitic effects while maintaining manufacturability.
4Ease of operation
If gate current is high, then the switch can be driven, but current drain increases
Solution Approach 1:
The insulated gate layer acts as an intermediary between the gate electrode and the semiconductor channel. This intermediate insulating layer blocks direct current flow between the gate and channel, dramatically reducing gate current drain while still allowing electric field control of the channel for effective switch driving capability.
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 achieves lower current drain, reduced size, lower insertion loss, and improved power handling while maintaining high isolation and fast switching times, effectively addressing the limitations of existing GaN switches in high-power RF applications.
Implementation Method 1
A switch is disclosed including an insulated gate that reduces the gate current
Implementation Method 2
using a multigate structure to handle higher voltages and reduce insertion loss
Implementation Method 3
Generation of a negative voltage requires many stages of charge pump circuits. Each stage of a charge pump requires a capacitor.
Data Source
AI summary
A HEMT cell includes two or more gallium nitride (“GaN”) high-electron-mobility transistor (“HEMT”) devices electrically connected in series with each other. The HEMT cell includes a HEMT cell drain, a HEMT cell source and a HEMT cell gate. The HEMT cell drain connects with the drain of a first GaN HEMT device in the series. The HEMT cell source connects with the source of a last GaN HEMT device in the series. The HEMT cell gate connects to a first two-dimensional electron gas (“2DEG”) gate bias resistor that connects with the gate of the first GaN HEMT device. The HEMT cell gate connects to a second 2DEG gate bias resistor that connects with the gate of the second GaN HEMT device. The first and second 2DEG gate bias resistors are located in a 2DEG layer of the HEMT cell. A multi-throw RF switch is also disclosed.