3. Vertical GaN Transistors for Power Electronics

The chapter titled “Vertical GaN Transistors for Power Electronics” takes the reader through the research and development cycle of GaN vertical-device technology, detailing out the three-terminal devices developed over the last decade. Power converters rely on solid state devices featuring diodes and transistors as their basic building blocks. GaN technology is an ever-expanding topic for R&D, proving its potential to solve several challenges in power conversion that cannot be addressed by Si. Medium-voltage (650–900 V) devices using the HEMT configuration have been able to reduce form factor at the system level by driving circuits at higher frequencies (100KHz–1 MHz) and eliminating heat sinks or reducing cooling requirements. Such potentials sparked the interest in GaN device research to address power conversion needs. However, in power conversion the demand of high current (50A and higher) from a single chip for a rated voltage (1KV and higher) is a standard requirement. Particularly when the market is favorable toward electrification of cars and other means of transportations, GaN must expand its scope to provide high power solutions with higher power density compared to Si and even SiC. Vertical devices have been the choice of power device engineers for economic use of the material and maximum use of its physical properties (which allow highest possible blocking field, field mobility, etc.). In this chapter, we discuss vertical transistors first in its normally on form (CAVETs) and then in its normally off design (MOSFET). The advantages and disadvantages are discussed for each type besides describing their operation principles. We have tried to make this chapter scholastic and informative by use of modeling and experimental data for each device we describe. The chapter will help the reader to realize the most recent status of GaN vertical transistors and appreciate its potential in power conversion.