R.F. Pierret

Dual-gate operation and volume inversion in n-channel SOI MOSFET's

The effects of volume inversion in thin-film short-channel SOI MOSFETs and the efficacy of dual-gate operation in enhancing their device performance have been analyzed using two-dimensional device simulations and one-dimensional analytical computations. The analyses have been restricted to the strong inversion regime, which is the practically useful region of operation of the SOI MOSFETs. In this region, the analyses suggest that when compared at constant V/sub G/-V/sub T/ values, the dual-channel volume inverted devices do not offer significant current-enhancement advantage, other than that expected from the second channel, over the conventional single-channel devices for silicon thicknesses in the 0.1- mu m range.<<ETX>>

Pseudomorphic ZnSe/n‐GaAs doped‐channel field‐effect transistors by interrupted molecular beam epitaxy

The fabrication and current‐voltage characteristics of the first depletion‐mode field‐effect transistors based on a pseudomorphic ZnSe/n‐GaAs heterointerface are described. The devices are doped‐channel field‐effect transistors produced by means of interrupted growth with the use of two separate molecular beam epitaxy systems. Very strong (visible to the naked eye) reflection high‐energy electron diffraction intensity oscillations persist for 120 periods when ZnSe is nucleated on the GaAs epilayer. The current‐voltage characteristics of the transistors are close to ideal; channel modulation indicates that the Fermi level is not pinned at the ZnSe/GaAs interface.

Surface acoustic wave resonators on a ZnO‐on‐Si layered medium

The adaptation of surface acoustic wave resonator technology to a ZnO‐on‐Si layered medium is presented. Several distributed reflector schemes are considered, including shorted and isolated metallic strips, as well as grooves etched in the ZnO layer. In the case of etched groove reflectors, a first‐order velocity perturbation arises due to the dispersive nature of the layered medium. Unique resonator design considerations result from the reflector array velocity and reflectivity characteristics. Transverse mode resonances are characterized and their effect on resonator response eliminated by a novel transducer design. A technique for temperature compensating the devices by use of a thermal SiO2 layer is discussed.

Aluminum nitride on silicon surface acoustic wave devices

Reactive rf planar magnetron sputtering has been used at substrate temperatures below 300 °C to deposit highly oriented piezoelectric AlN films on silicon for surface acoustic wave device applications. The substrates were (100)‐oriented, n‐type silicon with and without a thermally grown oxide. Several new AlM‐on‐silicon surface acoustic wave devices were fabricated and tested. The devices reported herein include two‐port delay lines, degenerate monolithic convolvers, and two‐port surface acoustic wave resonators utilizing metal strip reflector arrays.

Zinc‐oxide–on–silicon surface acoustic wave resonators

The first surface acoustic wave resonators fabricated using a ZnO‐on‐Si layered structure are described and characterized. The optimum location of the transducers in the resonant cavity and the general performance are first cited for devices containing isoloated aluminum, isolated Cr/Au, and shorted Cr/Au reflector strips. The transmission characteristics and reflecting properties of the shorted Cr/Au configuration are then examined in more detail. An unloaded Q of 3100 has been obtained with the shorted Cr/Au configuration at a resonant frequency of 105.4 MHz.

Deep levels in Ga-doped ZnSe grown by molecular-beam epitaxy

Results of a deep‐level transient spectroscopy study of Ga‐doped ZnSe thin films grown by molecular‐beam epitaxy are presented. Two prominent deep levels were observed in all the samples investigated. The concentration of the trap detected at 0.34 eV below the conduction‐band edge was essentially independent of the doping concentration and is attributed to native defects arising from Se vacancies in the ZnSe films. The second level with an activation energy of 0.26 eV shows a very strong doping dependence and is tentatively identified as arising from dopant‐site (gallium‐on‐zinc‐site) defects complexed with selenium vacancies. Preliminary results also indicate that planar doping of ZnSe significantly reduces the concentration of the Ga‐vacancy complex.

Interface transduction in the ZnO‐SiO2‐Si surface acoustic wave device configuration

Results are presented describing the operational behavior of a ZnO‐SiO2‐Si surface acoustic wave (SAW) device with a new transducer configuration. In the new configuration the transducer is positioned at the ZnO‐SiO2 interface; a metal overlays the transducer at the outer ZnO surface. The transduction loss in a SAW delay line is observed to vary by 30 dB when a dc voltage is applied to the interface transducer. This change in transduction with bias is cited as the basis for the possible construction of a new class of programmable devices. The lowest measured insertion loss is 20 dB, a value comparable to that obtained from conventional ZnO‐SiO2‐Si devices.

Sputtered Aluminum Nitride on Silicon for SAW Device Applications

Reactive rf planar magnetron sputtering is employed to deposit piezoelectric aluminum nitride films on silicon substrates where the substrate temperature during deposition is below 300°C. The films, grown on substrates of both (100) and (111) oreinted silicon with and without the presence of a thermally grown oxide, are oriented with the c-axis normal to the substrate surface. We report the operating characteristics of several new ALN-on-silicon devices. These include two-port delay lines , degenerate monolithic convolvers, and surface acoustic wave resonators utilizing metal strip reflector arrays. The reported data includes electrical characteristics of the metal-AIN-(SiOz)-Si sandwich, and dispersion properties for (100)-cut, -propagating and (111)-cut, -propagating substrates.

A new linear sweep technique to measure generation lifetimes in thin-film SOI MOSFET's

A new linear sweep technique to measure generation lifetimes (/spl tau//sub g/) in silicon-on-insulator (SOI) material is presented. A detailed analytic formulation is applied to fully-depleted and partially-depleted SOI films and used to simulate the behavior of the SOI devices under linear sweep conditions. A novel algorithm accurately determines the effective generation width in fully depleted SOI films. The measurement technique is experimentally verified by applying the algorithm to fully depleted SIMOX P-channel MOSFETs where observed lifetimes ranged from 0.3 /spl mu/s to 2.4 /spl mu/s. >

Induced junction monolithic zinc oxide‐on‐silicon storage correlator

An induced junction array is proposed as an alternative to the conventional PN diode configuration in the implementation of reference storage in a surface acoustic wave SAW storage correlator. Induced junction devices fabricated in the ZnO‐on‐Si structure are found to exhibit performance characteristics comparable to those of PN diode correlators, while providing greater ease of fabrication.