| Gallium nitride (GaN) semiconductor power devices can greatly lower the power consumption during on-state while blocking the same voltage in off-state, compared with the silicon devices that are commonly used today. GaN devices can also operate under much higher frequency than silicon devices, and thus can reduce the form factors of varies power systems, such as the power supply of portable electronic devices. This research focuses on the development of high-voltage GaN MOS-channel high-electron-mobility transistors (MOSC-HEMTs) for power switching applications. The research covers both the development of single discrete GaN devices, and the integration of GaN devices for future GaN integrated circuits (ICs). The high-voltage lateral GaN RESURF MOSC-HEMTs are designed using a novel approach by putting an undoped GaN cap layer on top of the AlGaN layer, and uses the negative polarization charges at the GaN cap/ AlGaN interface for charge compensation. Alternative method of incorporating negative fluorine atoms into the RESURF region using CF4 plasma treatment has also been explored. The devices are fabricated in the RPI cleanroom facilities and the experimental results are presented. Best Ron,sp of 4 mΩ-cm2 has been achieved with MOS channel lengths of 0.3 &mgr;m. Breakdown up to 840V has been achieved for the devices fabricated on a thick epi with total thickness of 4 microm with CF4 plasma treatment, and 350V for the devices on a thin epi of 1.8 microm with 20 nm GaN cap. High-voltage vertical GaN devices, such as a superjunction HEMT, have been designed using numerical simulations, projecting Ron,sp as low as 4.2 mΩ-cm2 with breakdown voltage of 12.4 kV. The monolithically integrated GaN LEDs and GaN power MOSC-HEMTs have been demonstrated with high temperature (225 oC) operation capabilities. This is the first demonstration of such technology in the world to the author's knowledge. The integration procedures have been presented and the experimental results have been shown. The integration can possibly be one of the basic building blocks of future light-emitting power ICs (LEPICs) for many smart lighting applications. |
