The rise of GaN on Si to take on high-power and high-volume markets
GaN itself comes in two main flavours, GaN on SiC which is ideal for very high power applications and GaN on Si which offers the ability to scale up in wafer diameter, driving costs down as volume rises, exploiting the traditional economies-of-scale offered by CMOS. MACOM expects GaN to disrupt all RF functions and applications.
GaN on Si as a wideband gap semiconductor technology in RF and microwave applications is becoming critical for mainstream commercial applications due to its power density, efficiency and thermal properties. GaN on Si offers 8x the raw power density of GaAs and 4x the raw power density of LDMOS technology. Efficiency ranges from the mid-40s to as much as 70%.
The market potential for GaN is big and the process technology is expected to eventually dominate the high performance RF and microwave market. GaN performance advantages include 5x bandwidth and 2x efficiency over existing products.
Furthermore, GaN is capable of fulfilling all analog functions and applications
GaN on SiC versus GaN on Si
Fundamentally, at a physics level, SiC boules grow 200x to 300x slower than silicon. Thus the cost of producing substrates scales proportionally to production time. For this reason GaN on SiC will remain too expensive for mainstream commercial use. However, it will find use in specialised applications in military and defence and potentially high end communications applications that require relatively high power.
The ability to reduce costs yet benefit from high power density and efficiency lies with GaN on Si. Further, GaN on Si is very complimentary to a silicon roadmap — and is expected to eventually accommodate a lot of CMOS on the die with it.
GaN on Si technology will be driven by power conversion applications, which command unit volumes that are orders of magnitude greater than RF and microwave demand.
According to John Croteau, President and CEO of MACOM, “Put in perspective, a full year’s production for the entire RF and microwave industry can be serviced in a few weeks by a single 8” silicon factory that’s built to service the power conversion market.”
The road to mainstream commercialisation
As GaN transitions from a niche, expensive process to a high-volume commercial process, the technical merits of GaN technology must be fully realized and clearly demonstrated on silicon substrates and, secondly, a scalable, stable supply chain must be established. GaN on Si has already demonstrated its technical merits in terms of power density and efficiency, easily beating GaAs and LDMOS. In the high end RF and microwave market power density and efficiency are critical considerations, hence the massive interest in GaN on Si.
Establishing a reliable and stable supply chain entails two key steps in the manufacturing chain: firstly, a cost-effective and scalable supply of GaN wafers is needed; secondly, the processing of these wafers through high-volume silicon fabs is needed.
To this end, MACOM recently announced an agreement with IQE, a leading supplier of GaAs, who will scale high-volume, cost-effective supply of GaN materials for cost sensitive, high-volume applications. IQE has the operational experience, competence and capital structure to scale production of GaN materials. MACOM also offer the industry’s only secure dual sourced GaN supply chain.
John Croteau contends that as with GaAs, we expect a bifurcation in the GaN supply chain for low volume applications. Cost-sensitive applications will go the path of 8” GaN on Si. At the same time, capital-lite fabs will service diverse, low-volume applications with specialty GaN processes.
“As much as 50% of GaN revenues today are attributable to government programs, not commercial production. Just as GaAs went from esoteric technology to high-volume market mainstay, GaN is now poised to do the same,” says John Croteau.
“At maturity, we believe that GaN on Si will benefit from silicon cost structures that are 3x lower than today’s highest volume GaAs and 100x lower cost than today’s GaN on SiC technology.
MACOM committed to driving GaN
MACOM holds 50 GaN device/materials patents and 200 U.S. and foreign patents. The company has positioned itself to drive GaN on Si to volume production eventually using 8” wafers. By leveraging the scale volume of the silicon industry, which is two orders of magnitude greater than even the GaAs handset market, MACOM expect to soon be able to leverage GaN for cost-sensitive applications.
A variety of packaging options, which support end market applications, is also a critical performance and cost factor which must be considered for a complete product implementation. Recently, the company has introduced surface mount plastic packaging for high power devices. Plastic packaged high power GaN enables designers to adopt conventional surface mount manufacturing and enables system size and weight reductions. In this way, the adoption of GaN in plastic facilitates system manufacturing cost reduction together with test efficiencies associated with high volume plastic packaging. The arrival of GaN in plastic devices has provided system designers the flexibility to reach power levels up to 90 W without the size or weight penalties typically associated with packaged transistors.
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