Scientists at KAUST have made an international effort to develop a radio frequency circuit component using an organic material with potential for 5G applications.
Organic semiconductors share many of the physical properties of their inorganic counterparts, such as silicon-based semiconductors, and are made using solvent-based processing techniques. This makes them cheaper and more flexible, but a major drawback is that electrical charges move more slowly in organic materials. According to KAUST (King Abdullah University of Science and Technology) in Saudi Arabia, this drawback is a barrier to adopting organic semiconductors for applications such as radio frequency electronics.
“Unlike their inorganic counterparts, organic semiconductors are inexpensive and easy to process through solution-based routes such as printing or knife-and-die coating,” said Ph.D. student Kalaivanan Loganathan, in collaboration with Thomas Anthopoulos. “To make this technology usable for the 5G frequency band, it is necessary to fabricate organic Schottky diodes.”
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The Schottky diode allows current to flow in one direction, but blocks current in the other. The main difference between the more ubiquitous pn diode and the Schottky diode is that it can switch from the conducting to the non-conducting state much faster, making them essential in radio frequency applications.
The speed of Schottky diodes is generally limited by device capacitance and resistance. But organic semiconductors are often associated with high capacitance and resistance due to their low charge carrier mobility. They are mostly used in conventional sandwich-type architecture in which the semiconductors, metals and electrical contacts are superimposed.
Loganathan and the team would have reinvented this device architecture and placed the two electrical connections side by side. The Organic Semiconductor – C16IDT-BT – was placed in a 25nm gap between the diodes, which gave the diodes ultra-low capacitance and resistance.
They showed that this Schottky diode worked up to a frequency of 6GHz. They were then able to expand this to 14 GHz by chemically doping the semiconductor with the addition of another molecule.
“Our results show that organic semiconductors are capable of operating in the 5G frequency range, just like their inorganic counterpart, with the added advantage of being able to be mass-manufactured at low cost using solution processing,” Loganathan said in a statement. .
The team wants to integrate their diodes into radio frequency circuits, ID tags and wireless energy harvesting devices. Their findings have been published online in Advanced materials†
