The power semiconductor market demands devices that show normally-off operation, which means that there is no current conduction when the transistor’s gate is set at 0V.

The natural form of GaN HEMTs (High Electron Mobility Transistors) is normally-on or so-called depletion mode (d-mode), which requires special drivers or to be placed in a cascode package solutions to realize normally-off operation.

Innoscience’s GaN HEMTs are intrinsically normally-off or so-called enhancement mode (e-mode) devices. The normally-off operation is realized by growing a p-GaN layer on top of the AlGaN barrier, deposition and patterning of a gate metal and then selective recessing the p-GaN layer over the AlGaN barrier.

The gate metal layer forms a (Schottky) contact with the p-GaN layer, and, as a consequence, the potential in the channel at the equilibrium is lifted-up therefore realizing normally-off/e-mode operation. 

Innoscience technology is optimized for high performance and reliability as well as for mass production and cost reduction. One of the key parameter defining the technology performance is the specific R_{DS_ON} that is the on-resistance per unit area (i.e. the smaller the specific R_{DS_ON} the smaller a device can be design for a given on-resistance; the smaller the device, the larger the number of devices that can be placed into a wafer and thus the lower the cost).

Innoscience has developed a strain enhancement layer technology, which consists of the deposition of a specific layer after the gate stack definition. The stress modulation created by the strain enhancement layer induces additional piezoelectric polarizations; this causes the 2DEG density to increase and thus the sheet resistance to decrease by 66% compared with a device without strain layer.

Since the strain enhancement layer is deposited after the gate formation, it only affects the resistance in the access region and it does not impact other device parameters such as threshold, leakage etc..

Thanks to this technology, Innosience’s GaN-on-Si e-mode HEMTs show very low specific on-resistance. 

Innoscience’s GaN technology is optimized for performance and reliability.

One of the key technology aspect of Innoscience’s GaN technology is the very low dynamic R_{DS_ON} over the full temperature and voltage range. This means that the on-resistance of the device does not increase when used in real power switching applications.

Not optimized GaN technology often shows a drift of the on-resistance when a high voltage is applied to the drain side of the device while the device is switched off, as the device would experience  in real application. This is not only detrimental for the overall system performance, as higher resistance means higher loss, but it is also detrimental for the device reliability as the device become hotter and more prone to failure.

This is one of the reason why Innoscience’s GaN technology shows excellent temperature stability in real application without overheating.

Innoscience has achieved this by carefully optimizing both epitaxy as well as device process technology.