A systematic investigation on Mg doped and undoped InGaN epilayers grown by plasma-assisted molecular beam epitaxy has been conducted. Single phase InGaN alloys across the entire composition range were synthesized and Mg was doped into InxGa1−xN (0.1 ≤ x ≤ 0.88) epilayers up to ∼1020/cm3. Hall effect, thermopower, and electrochemical capacitance voltage experimental results demonstrate the realization of p-type InGaN across the entire alloy composition range for properly Mg doped InGaN. Hole densities have been measured or estimated to be in the lower ∼1018/cm3 range when the net acceptor concentrations are in the lower ∼1019/cm3 range across the composition range.

A compact and high optical transmission touch screen has been developed using surface acoustic waves (SAWs) oscillated by ZnO thin-film piezoelectric transducers. It has a 98% optical transparency and a narrow frame of 1.4 mm. Therefore, it is ideally suitable for mobile devices, such as PDAs or cellular phones.Utilizing a single-phase transducer (SPT) constructed with a ZnO piezoelectric thin film sandwiched between a lower planar electrode and a comb-type electrode enabled us to reduce the ZnO film thickness to 1/20. The peculiarity of the ZnO transducer is using the local maximum of the electromechanical coupling factor with the SPT structure.It has been found that the hillocks on the lower electrode extremely affects the insertion loss and their suppression can improve the ZnO transducer quality. It is very helpful to introduce our own index, the area ratio of hillocks, to determine whether an aluminum alloy is suitable for the ZnO thin-film transducer or not.This paper describes the ZnO thin film we developed for the new SAW touch screen.

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This paper presents a low-cost packaged and reliable piezoelectric-actuated RF-MEMS switch for mobile communications. We fabricated a stiff single crystal silicon (SCS) beam that has an actuator and a contact bump on an SOI wafer without backside etching. We bonded the wafer to a ceramic cap wafer, directly packaging a switch with a contact gap of 0.5-μm not using sacrificial layers. The switch operated up to 1 billion cycles keeping a low insertion loss (<0.4 dB up to 5GHz) at 20-V driving voltage. The surface mountable SPST switch was 1.6 x 1.1 x 0.8 mm in size.