New type of transistor reaches 640 GHz
At extremely small feature sizes, High Electron Mobility Transistors (HEMTs) encounter a problem: The thinner the barrier material of InAlAs (indium aluminum arsenide) becomes, the more electrons flow from the charge-carrying channel through the gate. These unwanted gate leakage currents have a negative effect on the performance and lifetime of the transistor – making further transistor scaling impossible. The classic HEMT thus has reached its scaling limit with this transistor geometry. Conventional silicon MOSFETs are also familiar with this problem. However, they have an oxide layer that can prevent unwanted leakage currents for longer than is the case with the HEMT.
Researchers at Fraunhofer IAF now combined the advantages of III/V semiconductors and Si-MOSFETs and replaced the Schottky barrier of the HEMT with an insulating oxide layer. The result is a new type of transistor: the metal oxide semiconductor HEMT, MOSHEMT for short. According to Fraunhofer researcher Arnulf Leuther, this technology opens up the potential to scale HEMTs further and thus raise the cut-off frequency even further. For the start, Leuther and his team reached an oscillatator frequency of 640 GHz, setting a new record.
To overcome the increasing gate leakage currents, the researchers had to use a material with significantly higher barriers than the classical Schottky barrier. They replaced the semiconductor barrier material with a combination of insulating layers consisting of aluminium oxide (Al2O3) and hafnium oxide (HfO2). “This enabled us to reduce the gate leakage current by more than a factor of 1000. The first MOSHEMTs produced demonstrate a very high development potential, while existing FET technologies have already reached their limits,” reports Axel Tessmann, also a researcher at Fraunhofer IAF.
The ultra-fast MOSHEMT is designed for the frequency range above 100 GHz and is therefore of particular interest for novel communication, radar and sensor applications. In the future, such components will ensure faster data transmission between radio masts, enable imaging radar systems for autonomous driving and higher resolution and accuracy of sensors.
While it will be several years before the new type of transistor finds its way into industrial production, researchers at the Fraunhofer IAF have already gone one step further: They have succeeded in realizing the world’s first amplifier MMIC (Monolithic Microwave Integrated Circuit) based on InGaAs-MOSHEMTs for the frequency range between 200 and 300 GHz.
More news: https://www.iaf.fraunhofer.de/en.html
Related articles:
Record-setting HEMT promises cheaper, faster wireless communications
Multi-cell GaN-HEMT on single-crystal diamond
If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :
