Why RFIC Solutions  for GaN ?

RFIC Solutions GaN offers higher bandwidth, high power density, high operating voltage for improved system power efficiency. Stay tuned for upcoming RFIC Solutions GaN HPAs and front-end chips. RFIC Solutions has a design expertise for GaN in India.

GaN on SiC Fundamentals

GaN on SiC will remain the purview of low-volume, niche applications due to the inherent cost structure of substrate material. Fundamentally, at a physics level, SiC boules grow 200X to 300X slower than silicon . The cost of producing substrates – notably capital depreciation and energy consumption during material growth – scales proportionally to production time.  Thus, GaN on SiC will remain perpetually higher cost and therefore prohibitive for mainstream commercial use. Therefore, GaN on SiC production for the highest power density and defense applications will play to the strength of capital-lite fabs that aren’t exposed to the technology transitions that have affected the cellular handset market. 

The GaN on SiC provides the following Features

High electron mobility. GaN has an electron mobility approaching 2000 cm2/V·s, which is higher than LDMOS but lower than GaAs. GaAs’ higher electron mobility enhances operation at higher frequencies, however, GaN structures and processing continue to improve in the area of fmax.

Higher breakdown voltage. GaN devices are available for operation with VDS of 28 and 48 V, compared to 12 V for GaAs devices. LDMOS is available with the same operating voltages as GaN. High operating voltage results in lower drain current and lower resistive losses. Along with GaN’s internal structure, high voltage operation contributes to higher impedance and lower capacitance.

Higher power density. The GaN structure enables effective thermal conduction pathways, but the SiC substrate is also a primary contributor to high thermal performance. SiC has far better thermal performance than sapphire or silicon substrates that are also used in GaN devices. High power density allows operation at higher heat sink temperatures, simplifying cooling requirements. An obvious benefit is the safety factor for systems that are able to maintain typical operating temperatures.

Compact die size. The structure of a GaN HEMT (see Figure 3) allows straightforward implementation of passive components: thin film resistors, metal-insulator-metal (M-I-M) capacitors, and slot vias. The small size also contributes to the next characteristics in this list.

Lower input and output capacitances. Gate structure, compact size, high breakdown voltage, and straightforward interconnections all contribute to lower capacitances. AM-PM conversion, a significant distortion factor in wireless PAs, results primarily from variation in Ggs with voltage. The smaller gate periphery of GaN results in lower Cgs, less change versus voltage, and reduced AM-PM conversion than other devices.

Higher input and output impedances. Low capacitance and the higher resistive impedance resulting primarily from higher operating voltage result in higher impedances. This greatly simplifies matching, allowing simpler, lower loss circuits and enables wide bandwidth matching networks. In many cases, internal matching is not required, which is important for broadband applications. When a specific application area and frequency band is targeted, internal pre-matching can further simplify the design of matching circuitry.

Higher PAE. GaN’s slower growth in distortion as the device approaches saturation allows amplifiers to operate with less “backoff” from Psat. This behavior also supports effective implementation of linearization techniques like predistortion.