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Circular microdisk mechanical resonators vibrating in their various resonance modes have emerged as important platforms for a wide spectrum of technologies including photonics, cavity optomechanics, optical metrology, and quantum optics. Optically transduced microdisk resonators made of advanced materials such as silicon carbide (SiC), diamond, and other wide- or ultrawide-bandgap materials are especially attractive. They are also of strong interest in the exploration of transducers or detectors for harsh environments and mission-oriented applications. Here we report on the first experimental investigation and analysis of energetic proton radiation effects on microdisk resonators made of 3C-SiC thin film grown on silicon substrate. We fabricate and study microdisks with diameters of ∼48 µm and ∼36 µm, and with multimode resonances in the ∼1 to 20 MHz range. We observe consistent downshifts of multimode resonance frequencies, and measure fractional frequency downshifts from the first three flexural resonance modes, up to ∼-3420 and -1660 ppm for two devices, respectively, in response to 1.8 MeV proton radiation at a dosage of 10¹⁴/cm². Such frequency changes are attributed to the radiation-induced Young’s modulus change of ∼0.38% and ∼0.09%, respectively. These devices also exhibit proton detection responsivity of ℜ ≈ -5 to -6 × 10⁻⁶Hz/proton. The results provide new knowledge of proton radiation effects in SiC materials, and may lead to better understanding and exploitation of micro/nanoscale devices for harsh-environment sensing, optomechanics, and integrated photonics applications.

 

We report the use of suboxide molecular-beam epitaxy ( S-MBE) to grow β-Ga 2 O 3 at a growth rate of ∼1 µm/h with control of the silicon doping concentration from 5 × 10 16 to 10 19  cm −3 . In S-MBE, pre-oxidized gallium in the form of a molecular beam that is 99.98% Ga 2 O, i.e., gallium suboxide, is supplied. Directly supplying Ga 2 O to the growth surface bypasses the rate-limiting first step of the two-step reaction mechanism involved in the growth of β-Ga 2 O 3 by conventional MBE. As a result, a growth rate of ∼1 µm/h is readily achieved at a relatively low growth temperature ( T sub ≈ 525 °C), resulting in films with high structural perfection and smooth surfaces (rms roughness of <2 nm on ∼1 µm thick films). Silicon-containing oxide sources (SiO and SiO 2 ) producing an SiO suboxide molecular beam are used to dope the β-Ga 2 O 3 layers. Temperature-dependent Hall effect measurements on a 1 µm thick film with a mobile carrier concentration of 2.7 × 10 17  cm −3 reveal a room-temperature mobility of 124 cm 2  V −1  s −1 that increases to 627 cm 2  V −1  s −1 at 76 K; the silicon dopants are found to exhibit an activation energy of 27 meV. We also demonstrate working metal–semiconductor field-effect transistors made from these silicon-doped β-Ga 2 O 3 films grown by S-MBE at growth rates of ∼1 µm/h. 

We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow β-Ga2O3 at a growth rate of ∼1 μm/h with control of the silicon doping concentration from 5 × 1016 to 1019 cm−3 . In S-MBE, pre-oxidized gallium in the form of a molecular beam that is 99.98% Ga2O, i.e., gallium suboxide, is supplied. Directly supplying Ga2O to the growth surface bypasses the rate-limiting frst step of the two-step reaction mechanism involved in the growth of β-Ga2O3 by conventional MBE. As a result, a growth rate of ∼1 μm/h is readily achieved at a relatively low growth temperature (Tsub ≈ 525 ○C), resulting in flms with high structural perfection and smooth surfaces (rms roughness of <2 nm on ∼1 μm thick flms). Silicon-containing oxide sources (SiO and SiO2) producing an SiO suboxide molecular beam are used to dope the β-Ga2O3 layers. Temperature-dependent Hall effect measurements on a 1 μm thick flm with a mobile carrier concentration of 2.7 × 1017 cm−3 reveal a room-temperature mobility of 124 cm2 V−1 s −1 that increases to 627 cm2 V −1 s−1 at 76 K; the silicon dopants are found to exhibit an activation energy of 27 meV. We also demonstrate working metal–semiconductor feld-effect transistors made from these silicon-doped β-Ga2O3 flms grown by S-MBE at growth rates of ∼1 μm/h.