Method of the out-of-band rejection improvement of the AlN based surface acoustic wave filters

Abstract

AlN based surface acoustic wave (SAW) filters with an acoustic wavelength (λ) of 8 µm have been fabricated based on sputtered AlN films on sapphire. The acoustic velocity of 1-µm-AlN/Sapphire bilayer structure is 5536 m/s, 60% higher than that of LiNbO. The central frequency, insertion loss, out-of-band rejection, and bandwidth of fabricated AlN based two-port type SAW filters with a delay gap of λ are 692 MHz, 25.58 dB, 35.40 dB, and 2.7 MHz, respectively. The impact of delay gap on the performance of AlN based filters have been studied experimentally. By the analysis of frequency response of SAW filters with delay gaps of λ, 15λ, and 30λ with and without time gating technique, we find that increase the delay gap of AlN based SAW resonators can improve the out-of-band rejection effectively because of the reduction of electromagnetic coupling, with a cost of a little degradation of insertion loss due to the small propagation loss of AlN/Sapphire bilayer. When the delay gap is increased from λ to 15λ, out-of-band rejection of AlN based filters is increased by 4.75 dB, while the insertion loss is only increased by 0.81 dB. When the delay gap is further increased from 15λ to 30λ, the suppression of out-of-band rejection is not obvious.

Development and Application of SAW Filter

“…The advantage of silicon carrier wafers compared to sapphire or quartz is the heat extraction properties of silicon. Silicon conducts heat ~4 times better than sapphire and ~16 times better than quartz [ 84 ]. 2021 R. Ruby, in X proposes a new type of lithium lithium tantalate (LT) bonded to a silicon hybrid substrate (SiSAW), which has temperature compensation, good power handling performance, and can eliminate the generation between the LT/Si interface [ 29 ].…”

Nondestructive Determination of Young's Modulus of Interconnecting Thin Films by a Broadband Surface Acoustic Wave‐Interdigital Transducer

“…Electronic microdevices based on SAW propagation have drawn considerable attention. In practice, SAW-based devices, where ultrasonic waves are generated in piezoelectric crystals by means of IDTs, are widely applied in modern communication systems [11,12] and serve as active elements of various sensors, [13][14][15] as well as in microfluidic applications of SAW, [16,17] which have recently received increasing attention. Generally, in telecommunication applications, the operating frequencies of SAW devices are particularly high and can even reach several gigahertz.…”

Annihilation of Nanoscale Inversion Domains in Nitrogen-Polar AlN under High-Temperature Annealing

“…1−4 As a result, it serves as a promising building block in numerous devices including deep ultraviolet light-emitting diodes (LEDs), 5,6 laser diodes, 7 power electronics, 8 and RF filters. 9 Compared to other compound semiconductors, wurtzite AlN thin films possess either metal-or nitrogen-polarity along the caxis due to the noncentrosymmetric crystallographic orientation. Normally, uniform metal-polar III-nitride is utilized in optoelectronic or electronic devices due to better crystalline quality and smoother surface morphology.…”

“…Aluminum nitride (AlN) has earned strong recognition as an ultra-wide-band-gap semiconductor for its remarkable advantages of high breakdown field, strong spontaneous polarization field, high thermal conductivity, and high chemical stability. − As a result, it serves as a promising building block in numerous devices including deep ultraviolet light-emitting diodes (LEDs), , laser diodes, power electronics, and RF filters . Compared to other compound semiconductors, wurtzite AlN thin films possess either metal- or nitrogen-polarity along the c -axis due to the noncentrosymmetric crystallographic orientation.…”