Fig 1: GaN vertical schottky diode

Powdec K.K. today announced the successful development of a schottky diode with a high breakdown voltage of over 600 Volts (V) using the next generation semiconductor Gallium Nitride (GaN). In addition to the vertical schottky diodes being made on low-cost, large diameter sapphire wafers, a proprietary method was developed where the sapphire substate is removed, further improving the thermal conductance of the device. The on-resistance of this GaN diode is over 100 times smaller than existing silicon power diodes, resulting in the reduction of power losses by more than 50%. Powdec plans volume shipments of the schottky diodes by 2012.

Powdec’s new GaN schottky diode can be used in the power conditioning of solar power systems, motor drive circuits, as well as in inverter and power factor correction (PFC) circuits that are key in the power supply unit of servers and other equipment. The use of these GaN diodes, will dramatically lower the DC/AC conversion power losses. The replacement of the existing silicon power diodes by these GaN power diodes, results in a 15 to 30% reduction in emitted CO2. Powdec’s products will enable an accelerated adoption of smart grids throughout our societies (where power and information networks are tied together, and where individually generated electricity from solar power etc. is smoothly connected to the main power grid).

Fig 1: GaN vertical schottky diode after separation from substrate.

Product Features
1. Large diameter sapphire substrates are used, so devices can be manufactured at very low cost like LEDs.
2. At 620 V, a leak current of less than 1 mA/cm2 was achieved. So for a 10 A diode, leak current will be on the order of 20 A, which is one-tenth that of than other GaN devices.
3. The diode has a vertical structure and it doesn’t suffer current collapse as in lateral devices.
4. On-resistance is over 100 times smaller than that in silicon diodes, thus providing very low power losses.
5. The thickness of the diode is extremely thin at approx. 20 m (see Figure 2), which gives very low conduction resistance and thermal resistance. This provides the device with low power losses and higher operating temperatures as well as allowing reduced system size as less thermal components are needed.
6. The GaN shottky diode provides high-speed performance so high frequency operation is possible. This allows for a reduction in capacitors and inductors needed in the system, thus leading to smaller and lower cost sytems.