Si to GaN Semiconductors

Gallium nitride (GaN) is a material that can be used in the production of semiconductor power devices as well as RF components and light emitting diodes (LEDs). GaN has demonstrated the capability to be the displacement technology for silicon semiconductors in power conversion, RF, and analog applications.

Since the raise of the electronics age over a hundred years ago, power design engineers have been on a search for the ideal switch, which will rapidly and efficiently convert raw electrical energy into a controlled. Firstly the vacuum tube came into existence, but they were inefficient, as evidenced in the heat that they generate, and their large size and high cost, created limits to their ultimate use. Next, in the late ‘50s, the transistor gained widespread use; with its small size and better efficiency they appeared to be the “holy grail” and rapidly displaced tubes while creating enormous new markets unreachable by vacuum tube technology.

Silicon quickly became the material of choice for the semiconductor transistor, not only because of its fundamentally superior electrical properties, but it was also far less expensive to produce than the vacuum tube. The meteoric rise of the silicon transistor, and subsequently integrated circuits, continued throughout the 1970’s and 1980’s. “Moore’s Law” – which called for a doubling of the transistor’s performance with a lowering cost approximately every 18 months, created a synchronized drumbeat of new products with higher performance AND lower cost to the delight of the consumer. And, for power conversion, it was the silicon-based power MOSFET, which was the core of this rise.

As with the vacuum tube, silicon power MOSFETs have now reached the end of road in delivering better performance at a constantly declining cost. Fortunately, the quest for the ideal switch that has infinitely fast switching speed, no electrical resistance, and a lower cost, has not slowed and new base materials upon which to build high performance power conversion transistors and integrated circuits have emerged.

The leading candidate for taking electronic performance to the next level and a reactivation of positive momentum of Moore’s Law is gallium nitride. GaN’s ability to conduct electrons more than 1000 times more efficiently than silicon, while being able to be manufactured at a lower cost than silicon has now been well established. Silicon is out of gas, and a new, higher performing semiconductor material is emerging – GaN is on the rise.

Fortunately, the cost to produce a GaN device is inherently lower than the cost to produce a MOSFET device, since GaN devices are produced using standard silicon manufacturing procedures in the same factories that currently produce traditional silicon semiconductors, and the resulting devices are much smaller for the same functional performance. Since the individual devices are much smaller than silicon devices, many more GaN devices can be produced per wafer, thus forming a situation where GaN devices will always cost less to manufacture than their silicon counterparts. As GaN technology improves, the cost gap gets even wider.

In speed, temperature and power handling, gallium nitride is set to take over as silicon power devices reach their limits. GaN is the technology that will allow us to implement essential future cleantech innovations where efficiency is a key requirement.

The excitement about GaN stems from its unique material and electronic properties. GaN devices offer five key characteristics: high dielectric strength, high operating temperature, high current density, high speed switching and low on-resistance. These characteristics are due to the properties of GaN, which, compared to silicon, offers ten times higher electrical breakdown characteristics, three times the bandgap, and exceptional carrier mobility.

Taking advantage of these properties GaN Systems has successfully developed transistors with an on-resistance lower than attainable with silicon, and even better than a mechanical relay contact. This together with GaN’s inherent negligible charge storage, in turn permits the design of power switching circuits with formerly unheard of efficiencies, small size and very low heat losses. Using a unique proprietary custom island topology the company has enabled the designs to be transfered easily from silicon carbide based wafers to lower cost silicon wafers.