PhD defence by Martijn Sebastiaan Duraij

Title: Gallium Nitride Transistorsin Extreme Temperatures


Principal supervisor: Associate Professor Tiberiu-Gabriel Zsurzsan, Department of Electrical and Photonics Engineering, DTU, Denmark
Co-supervisor: Associate Professor Arnold Knott, Department of Electrical and Photonics Engineering, DTU, Denmark
Co-supervisor: Brian Engelbrecht Thomsen

Evaluation Board
Associate Professor Ziwei Ouyang, Department of Electrical and Photonics Engineering, DTU, Denmark
Professor Francis Patrick McCluskey, The University of Maryland, USA
Professor Hans-Peter Nee, KTH Royal Institute of Technology, Sweden

Master of the Ceremony
Senior Reseacher Osamu Takayama

In consumer electronics, the device operating temperature rarely exceeds 100°C, while in the oil and gas well intervention industry the ambient temperature can reach up to 200°C. Electronic components are not often rated and qualified for these extreme temperature environments. It is common practice to characterize off-the-shelf components and evaluate their performance in the desired operating temperatures before using them in circuit design. Gallium Nitride (GaN) based components shows the capability to operate in highly elevated temperatures.
In this study, market available GaN transistors are characterized and evaluated for use in switch mode power electronic circuits rated for extreme temperatures. The selected devices are first characterized using a curve tracer while the device under test (DUT) is placed in a thermal chamber. Parasitic elements of the DUT were analyzed from the mechanical build-up and verified with measurement results. Most importantly, GaN devices show an 18.2% increase in output capacitance at 225°C compared to 25°C which is of high importance in switched mode electronic designed.
With the information of the parasitic elements, a half bridge power stage was built and tested in an idle operation mode. A long (LDT) and a short (SDT) dead time strategy were applied while the power stage was heated up to 200°C ambient temperature. Here it was found that the idle operating loss could highly be minimized using the third quadrant operation of the GaN-FET.
A 50V to 5V at 1A synchronous buck type converter showed capabilities to operate at 175°C using GaN-FETs. In this converter, three dead time strategies were tested: SDT, LDT and adaptive dead-time (ADT). An ADT circuit was developed to change the dead-time within the switching cycle and making adjustments based on output current and temperature. In a static operation, the LDT showed the highest efficiency of 81.9% at maximum output power. The ADT circuit showed its superiority with a dynamic load modulated at 2kHz, where a reduction of 9.1% in operating temperature of the high side FET was achieved. At 175°C, ADT efficiency with a dynamic load was 77.9%.
A final iteration, in the form of a class D amplifier, was compared to a class AB linear type amplifier, to be used as a transmitter for an OFDM signal. The class D stage was optimized for high temperature operation by a prolonged dead-time to maximize efficiency. The class AB stage outperformed the class D stage in all signal integrity measurements, both at room temperature as well as 150°C. However, the class D stage showed more than double the efficiency with room for improvements in signal integrity. This points towards the conclusion that a class D stage is the preferred type considering expected component lifetime degradation due to self-heating.
It can therefore be concluded that GaN devices show their capability for use in extreme temperatures with the note that care must be taken towards the switching timings.



tor 29 sep 22
13:00 - 16:00


DTU Elektro
DTU Electro


The defence will take place in Building 308, auditorium 12 at DTU Lyngby Campus