arXiv subjects

Kapil Saha

Publications and source records attributed to Kapil Saha.

5 recordsLinked to original sources

arXiv2025

62.6 GHz ScAlN Solidly Mounted Acoustic Resonators

We demonstrate a record-high 62.6 GHz solidly mounted acoustic resonator (SMR) incorporating a 67.6 nm scandium aluminum nitride (Sc0.3Al0.7N) piezoelectric layer on a 40 nm buried platinum (Pt) bottom electrode, positioned above an acoustic Bragg reflector composed of alternating SiO2 (28.2 nm) and Ta2O5 (24.3 nm) layers in 8.5 pairs. The Bragg reflector and piezoelectric stack above are designed to confine a third-order thickness-extensional (TE) bulk acoustic wave (BAW) mode, while efficiently transducing with thickness-field excitation. The fabricated SMR exhibits an extracted piezoelectric coupling coefficient (k2) of 0.8% and a maximum Bode quality factor (Q) of 51 at 63 GHz, representing the highest operating frequency reported for an SMR to date. These results establish a pathway toward mmWave SMR devices for filters and resonators in next-generation RF front ends.

eess.SP↗

arXiv2025

High-performance solidly mounted bidimensional mode resonators (S2MRs) operating around 16 GHz

This paper reports on Solidly-Mounted Bidimensional Mode Resonators (S2MRs) utilizing 30% Scandium-doped Aluminum Nitride on Silicon Carbide, operating near 16 GHz. Experimental results show mechanical quality factors up to 380, electromechanical coupling coefficients of 4%, and an overall Figure of Merit (FOM=Q *kt2) exceeding 15. Additionally, Q Bode calculation is reported along with an analysis of the piezoelectric energy confinement coefficient showing the impact of thickness-to-wavelength ratio on the acoustic wave confinement. Finally, the devices demonstrate power handling capabilities greater than 20 dBm while achieving close impedance matching to 50 Ohm. These features make them strong candidates for commercial, military, and harsh-environment applications like satellite communications (SATCOM) and Active Electronically Scanned Arrays (AESA).

physics.app-ph↗

arXiv2025

Ku-Band AlScn-On-Diamond SAW Resonators with Phase Velocity above 8600 m/s

In this work, an Aluminum Scandium Nitride (AlScN) on Diamond Sezawa-mode surface acoustic wave (SAW) platform for RF filtering at Ku-band (12-18 GHz) is demonstrated. Thanks to the high acoustic velocity and low-loss diamond substrate, the prototype resonator at 12.9 GHz achieves a high phase velocity ($v_p$) of 8671 m/s, a maximum Bode-$Q$ of 408, and coupling coefficient ($k_{\mathrm{eff}}^2$) of 2.1%, outperforming high-velocity substrates such as SiC and sapphire by more than 20% in velocity. Resonators spanning 8-18 GHz are presented. The platform's high power handling above 12.5 dBm is also experimentally validated.

eess.SP↗

arXiv2024

ScAlN-on-SiC Ku-Band Solidly-Mounted Bidimensional Mode Resonators

This letter reports on Solidly-Mounted Bidimensional Mode Resonators (S2MRs) exploiting a highly-optimized Sezawa mode in 30% Scandium-doped Aluminum Nitride (ScAlN) on Silicon Carbide (SiC) and operating near 16 GHz. Experimental results demonstrate mechanical quality factors (Qm) as high as 380, Bode quality factors (QBode) approaching 500, electromechanical coupling coefficients (kt2) of 4.5%, an overall Figure of Merit (FOM = Qm kt2) exceeding 17, and power handling greater than 20 dBm for devices closely matched to 50 ohms. To the best of the authors' knowledge, S2MRs exhibit the highest Key Performance Indicators (KPIs) among solidly mounted resonators in the Ku band, paving the way for the integration of nanoacoustic devices on fast substrates with high-power electronics, tailored for military and harsh-environment applications.

eess.SY↗

arXiv2024

18 GHz Solidly Mounted Resonator in Scandium Aluminum Nitride on SiO2/Ta2O5 Bragg Reflector

This work reports an acoustic solidly mounted resonator (SMR) at 18.64 GHz, among the highest operating frequencies reported. The device is built in scandium aluminum nitride (ScAlN) on top of silicon dioxide (SiO2) and tantalum pentoxide (Ta2O5) Bragg reflectors on silicon (Si) wafer. The stack is analyzed with X-ray reflectivity (XRR) and high-resolution X-ray diffraction (HRXRD). The resonator shows a coupling coefficient (k2) of 2.0%, high series quality factor (Qs) of 156, shunt quality factor (Qp) of 142, and maximum Bode quality factor (Qmax) of 210. The third-order harmonics at 59.64 GHz is also observed with k2 around 0.6% and Q around 40. Upon further development, the reported acoustic resonator platform can enable various front-end signal-processing functions, e.g., filters and oscillators, at future frequency range 3 (FR3) bands.

physics.app-ph↗