Rakesh K. Lal

Direct water photoelectrolysis with patterned n-GaN

Direct photoelectrolysis of water was observed using a structured n-GaN photoanode, aqueous NaOH solution, and platinum cathode. The structured n-GaN was formed by selective area regrowth using metal stripes defined by photolithography. Gas evolution from both the n-GaN anode and the platinum cathode was observed under UV irradiation without external bias. The metal stripes eliminated current crowding and the n-GaN regrowth increased specific surface area. As a result, distinct improvements in photocurrent were achieved. The origin of the photocurrent and the conversion efficiency are discussed based on water-splitting reactions and etching reactions.

600 V JEDEC-qualified highly reliable GaN HEMTs on Si substrates

In this paper, we demonstrate 600 V highly reliable GaN high electron mobility transistors (HEMTs) on Si substrates. GaN on Si technologies are most important for the mass-production at the Si-LSI manufacturing facility. High breakdown voltage over 1500 V was confirmed with stable dynamic on-resistance (RON) using cascode configuration package. These GaN HEMT on Si based cascode packages have passed the qualification based on the standards of the Joint Electron Devices Engineering Council (JEDEC) (1-5) for the first time. High voltage acceleration test was performed up to 1150 V. Even considering most conservative failure mechanism, mean time to failure (MTTF) of over 1×107 hours at 600 V was predicted at 80°C. Additional conclusion is that conventional packages such as TO-220 are still suitable for high speed circuit application without using a specific gate driver. Ultimately GaN will significantly reduce conversion losses endemic in all areas of electricity conversion, ranging from power supplies to PV inverters to motion control to electric vehicles, enabling consumers, utilities and governments to contribute towards a more energy efficient world.

Commercialization and reliability of 600 V GaN power switches

The reliability of 600 V GaN power switches, fabricated in a silicon CMOS foundry, has been demonstrated. JEDEC qualification of cascode packages and the long term reliability of GaN power switches has been estimated for the first and shown to be greater than a million hours. Excellent switched/dynamic on-resistance up to 1000 V and breakdown voltage over 1500 V indicate the suitability of these devices for switching up to 480 V. Detailed data of high temperature reverse bias (HTRB) test is shown. High temperature DC stress test and high voltage off-state stress tests also corroborate the high reliability of these devices. This suite of initial, JEDEC & accelerated stress tests show that GaN-on-silicon power switches are ready for many commercial and industrial applications, would significantly reduce switching losses and system size and will impact all areas of electricity conversion, ranging from tablet chargers to photovoltaic inverters and electric vehicles.

650 V Highly Reliable GaN HEMTs on Si Substrates over Multiple Generations: Matching Silicon CMOS Manufacturing Metrics and Process Control

Manufacturing readiness of the worlds first highly reliable 650V GaN HEMT is demonstrated with high process capability (CpK>1.6) for leakage and on resistance. This technology was developed in a Si-CMOS compatible 6-inch foundry and has been demonstrated with over one thousand wafers worth of data spread over two generations of technology nodes covering multiple products and packages collected during ramp up post qualification. Silicon manufacturing processes are employed including gold-free processes that avoid the use of evaporation/liftoff typical to compound semiconductors. Probe yield and Line yield for the GaN process now matches mature Si-CMOS process running in the same fabrication facility. Extended qualification results beyond JEDEC standard are also shown for GaN products for the first time. Products in cascode configuration were tested. Wide bandgap high speed and high voltage GaN devices significantly reduce the system size and improve energy efficiency of power conversion in all areas of electricity conversion, ranging from PV inverters to electric vehicles making the above results significant and making GaN high volume production a reality.