Power Electronic Devices
Semiconductor power electronic devices convert DC to AC power, and vice versa. They are found in battery chargers of laptops and mobile phones, in converters used to feed energy from solar cells into the energy grid, electric cars and many other applications. Energy losses in this conversion are obviously not wanted, but are unavoidable. While the best current Si-based devices have energy efficiencies of around 97 to 98%, and 2-3% energy loss sounds minimal, further improvements could result in benefits on the scale of entire power stations (coal, gas, nuclear).
Furthermore if these devices could be operated at a higher temperature than current Si technologies, they could be directly mounted onto engines such in an electrical car or an airplane engine, which would allow more convenient designs - in which Si based technology has already met its limits.
GaN-on-Si substrate power devices have emerged as an excellent alternative to Si based power electronics, allowing lower on-state resistance, operation at higher frequencies with minimal energy loss and the ability to operate at a higher temperature. They are competing not only with traditional Si devices, but also SiC and diamond technology.
Challenges nevertheless remain; the electrical performance of these devices should not degrade when they undergo fast switching, the so-called dynamic Ron issue. The responsibility lies with electronics traps in the devices, which get charged and de-charged, mostly in the GaN buffer layer and at device surface.
CDTR have been developing novel experimental techniques complemented by device simulation, to gain a unique physical understanding of the impact of electronic traps on dynamic Ron - and other - device parameters, and to find better ways to mitigate these effects. The knowledge gained through our research has the potential to contribute to intelligent device design in the future.
Figure 1. Normalized Dynamic on-Resistance measurements on 2 commercial devices from 2 different manufacturers. Ref: S. Karboyan, M. J. Uren, Manikant, J. W. Pomeroy, M. Kuball; "On the origin of Dynamic Ron in Commercial GaN-on-Si HEMTs", Microelectronics Reliability, October 2017.