Modular GaN HEMT Circuit for High Voltage Operation
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Solution Overview
Problem
High electron mobility transistors (HEMTs) face complications and mechanical stress when operating at voltages above 650 V on GaN-on-Silicon substrates, making it challenging to design high voltage circuits for commercial production due to the need for thicker buffer layers and potential wafer warpage.
Innovation Solution
A modular circuit design is implemented using a high-side depletion-mode transistor and a low-side enhancement-mode transistor, coupled with a variable capacitor and diodes, allowing for easier scaling to higher operating voltages without requiring new or complex processing technologies. The variable capacitor and diodes can be implemented using AlGaN technology and occupy no more than 20% of the die area, with the option to be on a separate die for modular construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the buffer layer is made significantly thicker to operate at voltages higher than 650 V, then the transistor can withstand higher voltages, but mechanical stress increases causing wafer warpage
Solution Approach 1:
The patent divides the high voltage circuit into multiple transistors operating in series, where each transistor operates at a lower voltage (below 650 V) rather than using a single transistor that must withstand the full high voltage. This segmentation allows each transistor to use a thinner, less stressed buffer layer while collectively achieving the required high voltage operation.
Solution Approach 2:
The patent changes the operational parameters of the transistor circuit by using multiple transistors with lower individual voltage ratings instead of a single transistor with a high voltage rating. This parameter change allows each transistor to operate within safe buffer layer stress limits while achieving the desired overall high voltage capability through series connection.
2Reliability
If a single high voltage transistor is used to operate above 650 V, then the circuit can achieve high voltage operation, but the design becomes more complicated
Solution Approach 1:
The patent segments the high voltage function across multiple standard-voltage transistors connected in series. Each transistor uses conventional design approaches with standard buffer layers, avoiding the need to develop complex new high-voltage transistor structures. The series connection of simpler transistors achieves the same functional result as a single complex high-voltage transistor.
Solution Approach 2:
The patent uses universal, standard-voltage transistor designs that can be manufactured using existing processes for multiple functions. By connecting these universal transistors in series, the system achieves high voltage operation without requiring specialized high-voltage transistor designs, thereby reducing design complexity and leveraging existing manufacturing capabilities.
3Reliability
If GaN bulk substrate or substrate removal is used to achieve high voltage operation, then voltage capability is improved, but manufacturing difficulty increases for commercial production
Solution Approach 1:
The patent segments the voltage handling function across multiple transistors on standard GaN-on-Silicon substrates, eliminating the need for complex substrate removal or GaN bulk substrate processes. Each transistor operates at a lower voltage that can be achieved with conventional buffer layers on standard substrates, making the process commercially manufacturable while still achieving high overall voltage capability through series connection.
Solution Approach 2:
The patent uses copies of standard-voltage transistor designs rather than creating a new high-voltage transistor design. By replicating conventional transistor structures in series, the system achieves high voltage operation using proven, commercially-manufacturable processes instead of requiring difficult-to-produce GaN bulk substrates or substrate removal techniques.
Data Source
AI summary
In an aspect, a circuit can include a first HEMT, a second HEMT, and a variable capacitor. A drain of the first HEMT can be coupled to a source of the second HEMT. An electrode of the variable capacitor can be coupled to a source of the first HEMT, and another electrode of the variable capacitor can be coupled to a gate of the second HEMT. In another aspect, an electronic device can include a die including a HEMT and a variable capacitor. An electrode of the variable capacitor can be coupled to a source or a gate of the HEMT, and another electrode of the variable capacitor can be coupled to an external terminal of the die. In a further aspect, an electronic device comprising a die, wherein the die includes a variable capacitor, a first diode, and a second diode.