What is GaN? Gallium Nitride (GaN) Semiconductors Explained

What is GaN-on-silicon?

Gallium nitride (GaN) is a very hard, mechanically stable wide bandgap semiconductor. With higher breakdown strength, faster switching speed, higher thermal conductivity and lower on-resistance, power devices based on GaN significantly outperform silicon-based devices. Gallium nitride crystals can be grown on a variety of substrates, including sapphire, silicon carbide (SiC) and silicon (Si). By growing a GaN epi layer on top of silicon, the existing silicon manufacturing infrastructure can be used eliminating the need for costly specialized production sites and leveraging readily available large diameter silicon wafers at low cost.

GaN is 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.

What is GaN HEMT?

High electron mobility transistors (HEMTs) are transistors that use a 2-dimensional electron gas (2DEG) that is created by a junction between two materials with different band gaps. Gallium nitride (GaN) based HEMTs feature faster switching speed, higher thermal conductivity and lower on-resistance than comparable silicon-based solutions. These features allow GaN transistors and integrated circuits to be used in circuits to increase efficiency, shrink the size, and reduce the cost of a wide variety of power conversion systems.

Since the dawn of the electronics age over a hundred years ago, power design engineers have been on a quest for the ideal switch, one that will rapidly and efficiently convert raw electrical energy into a controlled, useful flow of electrons.  First came the vacuum tube but inefficiency, 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 Transistors and the Electronics Age

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 1970s and 1980s. “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 the road in delivering better performance at a consistently 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.

Rise of Gallium Nitride Semiconductors

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 always cost less to manufacture than their silicon counterparts. As GaN technology improves, the cost gap gets even wider.

How does gallium nitride work?

Gallium nitride (GaN) is a wide bandgap semiconductor used for high-efficiency power transistors and integrated circuits. By growing a thin layer of aluminum gallium nitride (AlGaN) on top of a GaN crystal, a strain is created at the interface that induces a compensating two-dimensional electron gas (2DEG) This 2DEG is used to efficiently conduct electrons when an electric field is applied across it. This 2DEG is highly conductive, in part due to the confinement of the electrons to a very small region at the interface. This confinement increases the mobility of electrons from about 1000 cm2/V·s in unstrained GaN to between 1500 and 2000 cm2/V·s in the 2DEG region. This high mobility produces transistors and integrated circuits that feature higher breakdown strength, faster switching speed, higher thermal conductivity and lower on-resistance than comparable silicon solutions.

The Age of GaN is Underway

With the increase in transistor and IC performance made possible by GaN materials, now is the time for innovative power design engineers to take advantage of GaN attributes:

• lower on-resistance giving lower conductance losses
• faster devices yielding less switching losses
• less capacitance resulting in fewer losses when charging and discharging devices
• less power needed to drive the circuit
• smaller devices taking up less space on the printed circuit board
• lower cost

Use our interactive parametric selection tool to identify the best possible GaN solution for your power conversion system.