During this week’s PCIM Europe, Clifton GmbH unveiled a unique epitaxy (epi) technology to produce high-voltage Gallium Arsenide (GaAs) semiconductor material for diodes, transistors and intelligent power modules. The new GaAs devices offer higher performances, more efficiency and reliability in smaller and lighter devices; all at lower manufacturing costs/prices compared to SiC and GaN products. The company’s initial product is a 600V 15A PIN diode; and within 2 month, the company will add a 1200V device. The 600V device is offered as a 3.1mm chip for packaging into modules (such as those produced by Clifton’s partner, Powersem GmbH) and in a TO247-2 package. Target applications for these PIN diodes include high-power switching power supplies, power factor correction circuits, solar inverters and uninterruptible power supplies.
"We expect to offer our GaAs devices for half the cost of comparable GaN devices," commented Dr. Gerhard Bolenz, Clifton's CFO. "We have plans to ramp up to 6-inch epi over the next 12 months that will allow us to drive costs and prices down for our high-power and high-performance devices," he concluded.
Dr. Volker Duded, Clifton's CTO, continued: "Our technology can handle 100A in a single 1200V die. That same level of current would require 3 to 4 dice in SiC technology. And our GaAs epi offers several performance advantages: These GaAs PIN diodes have a junction capacitance of 20pF, over 10-times lower than Schottky devices and the Qrr of our current devices is only 500 nC and 25 degrees C and 650nC at 125 degrees C. In our next-generation devices, we will reduce the Qrr to less than half of those values," he concluded.
Clifton shared their product road map with PowerPulse and it includes: in the balance of 2014 the introduction of both ultra-fast diodes and higher-voltage diodes (up to 1700V); in 2015 the introduction of 600V heterojunction bipolar devices followed by "extreme-speed" 1200V diodes; and in 2016 the introduction of 1200V heterojunction bipolar devices followed by the introduction of "UBHT Isolated-gate" 1200V heterojunction devices.
Finally, Clifton shared a technology comparison of their GaAs epi devices compared with today's state-of-the-art silicon devices. The GaAs devices offer 2X higher critical electric field capability, 6X better carrier mobility, 1/7th the turn-off losses, 7X faster switching frequency, and emi generation and production cost structures both similar to silicon.
To product its GaAs devices, Clifton has developed a proprietary liquid phase epitaxy (LPE) crystal growth technique involving the near equilibrium growth of GaAs and other compounds from a saturated solution that is placed in contact with a polished substrate, generally GaAs. Just before or just after the surface of the substrate has been coated, the temperature is lowered from the equilibrium temperature at a controlled rate bringing on super saturation of the solution and leading to precipitation and epitaxial growth of the dissolved material onto the substrate.
The basic idea of LPE technology is not revolutionary in principle but in reality it is very sensitive to production-applied handling and is thus regarded as extremely demanding in industrial deployment. Clifton has successfully implemented the industrially challenging Liquid Phase Epitaxy (LPE) processing technology, solved all its technical hurdles, improved the technology, achieved control over the gallium arsenide crystal growth process and deployed it into production of high-voltage gallium arsenide p-i-n structures.