Nanoelectronics research centre Imec has developed 200V and 650V normally-off/enhancement mode (e-mode) on 200mm GaN-on-Silicon wafers, achieving below 20% dynamic Ron dispersion.

Imec's GaN-on-Si device technology is Au-free and compatible with the wafer handling and contamination requirements for processing in a Si fab. A key component of the GaN device structure is the buffer layer, which is required to accommodate the large difference in lattice parameters and thermal expansion coefficient between the AlGaN/GaN materials system and the Si substrate.

Imec_GaN-on-Si_01 (cr) Figure 1: Dynamic RDS-ON dispersion (10µs on – 90µs off)of imec’s 650V GaN-on-Si e-mode device technology measured at 25°C and 150°C. (Source: Imec)

The research centre said it achieved a breakthrough development in the buffer design (patent pending), allowing to grow buffers qualified for 650V on 200mm wafers. This, in combination with the choice of the Si substrate thickness and doping increased the GaN substrate yield on 200mm to competitive levels, enabling low-cost production of GaN power devices.

Imec_GaN-on-Si_02 (cr) Figure 2: Transfer characteristic of 36mm gate width imec’s 650V GaN-on-Si e-mode transistors. (Source: Imec)

Imec_GaN-on-Si_03 (cr) Figure 3: Leakage characteristic at VGS=0V of 36mm gate width imec’s 650V GaN-on-Si e-mode transistors. (Source: Imec)

The cleaning and dielectric deposition conditions have also been optimised, and the field plate design has been extensively studied. As a result, the devices exhibit dynamic Ron dispersion below 20% up till 650V over the full temperature range from 25°C to 150°C, according to Imec. This means that there is almost no change in the transistor on-state after switching from the off-state, a challenge typical for GaN technology.

Imec_GaN-on-Si_04 (cr) Figure 4: Typical output characteristic and transfer characteristic of 36mm gate width imec’s 650V GaN-on-Si e-mode device technology. (Source: Imec)

The technology is ready for prototyping, customised low-volume production and technology transfer, according to Imec.