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Pyroelectric-Like Response of III-V Semiconductors for Microelectronic Sensor Applications
Nam-IhnCho,YuriM.Poplavko,SeungJeongNoh 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.6
The multi-function possibilities of GaAs and other III-V semiconductor crystals have been expanded to microelectronic sensor applications by decreasing the symmetry of the crystal electric response. Under anisotropic boundary conditions, wide band-gap III-V semiconductors exhibit a pyroelectric crystal behavior (in spite of their being piezoelectric only). The partial strain limitation makes it possible to obtain a strong electric response on a scalar external stimulus, such as hydrodynamic pressure or change of temperature, in the [111]-planes of these crystals. A new symmetry eect forms a basis to fabricate a single-crystal pyroelectric or piezoelectric sensor array based on III-V crystals. In feasible sensor devices, the transducer, the amplier, and the read-out electronics will be fabricated on single crystal chip. The voltage sensitivity of a semi-insulating GaAs-type temperature sensor is on the same order as the voltage sensitivity for PZT pyroelectric ceramic sensors.
Jeong, Moongi,Kim, Beomjin,Poplavko, Yuriy,Kazmirenko Victor,Prokopenko Yuriy,Baik, Sunggi The Korean Ceramic Society 2005 한국세라믹학회지 Vol.42 No.7
A waveguide method is developed to study the materials with relatively large dielectric constants at microwave range. Basically, the method is similar to the previous waveguide methods represented by short-circuit line and transmission/reflection measurement methods. However, the complex permittivity is not determined by the shift in resonance frequencies, but by numerical analysis of measured scattering parameters. In order to enhance microwave penetration into the specimen with relatively large permittivity, a dielectric plate with lower permittivity is employed for impedance matching. The influences of air gap between the specimen and waveguide wall are evaluated, and the corresponding errors are estimated. The propagation of higher order modes is also considered. Experimental results for several reference ceramics are presented.
Piezo-controlled Dielectric Phase Shifter
Victor Kazmirenko,Yuriy Poplavko,Moongi Jeong,Beomjin Kim,Yuriy Prokopenko,Sunggi Baik 한국전자파학회JEES 2006 Journal of Electromagnetic Engineering and Science Vol.6 No.1
A sandwich structure of dielectric material and air gap inside a rectangular waveguide is proposed as a fast electrically tunable low-loss phase shifter. As the dielectric material is shifted up and down by piezoelectric actuator and, thereby, the thickness of air gap is changed, the effective dielectric constant of the sandwich structure is varied. Phase shifters based on the sandwich structure with different dielectric materials showed phase shift of 20~200˚/㎝ at X-band as the thickness of air gap varied up to 30 ㎛. The idea can be extended toward low-loss millimeter wave phase shifters since modern microwave ceramics have been developed to show very low dielectric loss(tanδ~10<SUP>-4</SUP>).