Gallium Nitride On Silicon Research Articles

A 17.3–20.2-GHz GaN-Si MMIC Balanced HPA for Very High Throughput Satellites

This letter presents the design and experimental characterization of a K-band high power amplifier (HPA) monolithic microwave-integrated circuit (MMIC) for the next generation of very high throughput satellites (vHTS). The MMIC is a three-stage balanced amplifier realized on a commercial 100-nm gate length gallium nitride on silicon (GaN-Si) technology. The design is compliant with space reliability constraints and, despite the larger thermal resistance and losses shown by the silicon (Si) substrate with respect to the more common silicon carbide (SiC), the realized HPA delivers, in pulsed condition, a peak output power larger than 41 dBm in the operative band from 17.3 to 20.2 GHz, with an associated power added efficiency (PAE) and gain up to 40% and 26 dB, respectively. In continuous wave (CW) operative conditions and with a backside temperature of 85 °C, the MMIC delivers a minimum output power and PAE of 39.4 dBm and 28%, respectively. Moreover, a 24-h test at saturated power has shown almost negligible performance degradations, thus providing confidence in the selected GaN-Si technology's robustness.

Vertical breakdown of GaN on Si due to V-pits

Gallium nitride on silicon (GaN/Si) is an important technological approach for power electronic devices exhibiting superior performance compared to devices based on a pure silicon technology. However, the material defect density in GaN/Si is high, and identification of critical defects limiting device reliability is still only partially accomplished because of experimental difficulties. In this work, atomic force microscopy, scanning electron microscopy, secondary ion mass spectrometry, and cathodoluminescence were employed to investigate commonly occurring epitaxial overgrown V-pits and inhomogeneous incorporation of oxygen and carbon across layer stacking in the vertical direction. These experiments identified V-pits as regions with higher n-type carrier concentrations and paths for vertical leakage through the buffer, as directly probed by conductive atomic force microscopy. The deleterious effect of V-pits on device performance is demonstrated by evaluating test devices fabricated on two wafers with significantly diverse density of buried V-pits induced by varying growth conditions of the aluminum nitride nucleation layer. A clear correlation between observed vertical breakdown and density of V-pits within the C-doped GaN layer below the device structures is obtained. Back-gating transient measurements also show that the dynamic device behavior is affected by the V-pit density in terms of the detrapping time constants.

A MMIC power amplifier in GaN on Si technology for next generation Q band high throughput satellite systems

this paper deals with the design, realization and test of a Microwave Monolithic Integrated Circuit (MMIC) power amplifier (PA) for next generation Q-band high throughput satellite systems. The MMIC, based on a four-stage architecture, was realized on a commercial 100 nm gate length Gallium Nitride on Silicon (GaN-Si) process. Accounting for the peculiarities of the selected technology, especially the lossy substrate and the relevant thermal resistance, particular care was devoted to identify effective circuital solutions able to mitigate the insertion loss of the matching networks and the temperature increase in the active devices. Experimental results carried out directly on-wafer show that the PA can achieve a saturated output power of roughly 36dBm with a gain and a power added efficiency higher than 20 dB and 23%, respectively, in the operative band from 37.5 GHz to 42.5 GHz. The chip area is 3.54 × 3.5 mm2. Such results are close to others state-of-art PAs realized in more expensive GaN processes based on Silicon Carbide, thus demonstrating that high resistivity Silicon substrate can be efficiently adopted also in such a peculiar application.