B. A. Vojak

Microplasma devices fabricated in silicon, ceramic, and metal/polymer structures: arrays, emitters and photodetectors

Recent advances in the development of microplasma devices fabricated in a variety of materials systems (Si, ceramic multilayers, and metal/polymer structures) and configurations are reviewed. Arrays of microplasma emitters, having inverted pyramidal Si electrodes or produced in ceramic multilayer sandwiches with integrated ballasting for each pixel, have been demonstrated and arrays as large as 30 ? 30 pixels are described. A new class of photodetectors, hybrid semiconductor/microplasma devices, is shown to exhibit photoresponsivities in the visible and near-infrared that are more than an order of magnitude larger than those typical of semiconductor avalanche photodiodes. Microdischarge devices having refractory or piezoelectric dielectric films such as Al2O3 or BN have extended lifetimes (~86% of initial radiant output after 100?h with an Al2O3 dielectric) and controllable electrical characteristics. A segmented, linear array of microdischarges, fabricated in a ceramic multilayer structure and having an active length of ~1?cm and a clear aperture of 80 ? 360??m2, exhibits evidence of gain on the 460.3 nm transition of Xe+, making it the first example of a microdischarge-driven optical amplifier.

Temperature dependence of threshold current for quantum‐well AlxGa1−xAs‐GaAs heterostructure laser diodes

Data are presented showing that the threshold current density Jth(T) of quantum‐well AlxGa1−xAs‐GaAs heterostructure laser diodes, grown by MO‐CVD, is less temperature dependent than that of conventional DH lasers. T0 in the usual expression Jth∝exp(T/T0) can be high as 437 °C. This behavior is explained in terms of the steplike density of states and the disturbed electron and phonon distribution functions of the quantum‐well active region.

Temperature dependence of threshold current for a quantum-well heterostructure laser

Abstract The threshold current density, J th , of a quantum-well laser diode is calculated taking into account the quasi-two-dimensional nature of the heterostructure. The calculated value of J th ( T ) for a quantum-well laser diode is found, in agreement with experiment, to be less temperature sensitive than that of a conventional double heterojunction laser. The step-like densities of states and the perturbed (hot) carrier distribution of a quasi-two-dimensional structure are responsible for the weaker temperature dependence. Supporting data on quantum-well Al x Ga 1- x AsGaAs heterostructure laser diodes grown by MO-CVD are presented showing that in the conventional expression J th ( T ) = J th (0) exp ( T / T 0 ), T 0 can be as high as ∼ 437°C.

Roadmapping disruptive technical threats and opportunities in complex, technology-based subsystems: The SAILS methodology

Abstract A heuristic methodology, based on observations of past patterns of change across several complex, technology-based, subsystem-level industries, is presented for the identification of potentially disruptive technologies. This methodology can be used to both guide the intuition of the senior technical visionary and aid in the formation of the intuition of more junior technologists as they develop the insight required to predict the future of technology. The five components of this methodology are recurring contributors to disruption at the subsystem level of the value chain: standards, architectures, integration, linkages, and substitutions (SAILS). The SAILS methodology is elucidated by applying it, both retrospectively and prospectively, to three complex, technology-based, subsystem-level examples: frequency generation subsystems in wireless communication supersystems; optical multiplexing subsystems in optical communication supersystems; and high voltage electrical subsystems in automotive supersystems.

LPE In1−xGaxP1−zAsz (x∼0.12, z∼0.26) DH laser with multiple thin‐layer (<500 Å) active region

A liquid‐phase‐epitaxial (LPE) double‐heterojunction (DH) laser structure with an ∼1‐μm ’’active region’’ consisting of ≳20 In1−xGaxP1−zAsz and InP lattice‐matched thin layers is described. The thin‐layer dimensions are small enough (<500 A) to make quantum size effects relevant.

Phonon‐assisted recombination and stimulated emission in quantum‐well AlxGa1−xAs‐GaAs heterostructures

Extensive data are presented on various photopumped multiple‐quantum‐well AlxGa1−x As‐GaAs heterostructures, grown by metalorganic chemical vapor deposition, showing the variety of laser operation that can be observed one and two phonons below the lowest (n=1, n′=1′) confined‐particle electron‐to‐heavy‐hole (e→hh, n) and electron‐to‐light‐hole (e→lh, n′) recombination transitions. These experiments are performed on small cleaved rectangular samples that, because of two identifiable sets of orthogonal coupled modes, permit unambiguous identification of laser operation on LO‐phonon sidebands below the confined‐particle transitions. For a small number (two) of closely coupled (∼50 A) GaAs quantum wells of size Lz ∼50 A laser operation occurs on multiples of h/ωLO from one phonon below transition n=1 (E1) to within a phonon or two of the L indirect band edge. AlxGa1−x As‐GaAs heterostructures with more coupled GaAs quantum wells readily permit observation of laser operation two phonons below the lowest confin...

Examining the Technical Corporate Entrepreneurs' Motivation: Voices from the Field

Prior research has proposed five conditions that support corporate entrepreneurship: rewards, management support, resources including time, organizational structures (at the macro level), and risk acceptance. This article investigates the sufficiency of these conditions in motivating individual scientists or engineers who have created and commercialized multiple breakthrough innovations in mature corporations—or technical corporate entrepreneurs. Using in–depth interviews with technical corporate entrepreneurs and human resource managers, we explore both how they are motivated and whether there is concurrence between how they say they are motivated and how their human resource managers perceive that they are motivated. We find the framework applicable but incomplete relative to motivating these individuals. The additional dimensions of appropriate work design (at the micro level) and their intrinsic motivation to innovate need to be considered in supporting technical corporate entrepreneurship. Further, we find that an important disparity exists between what technical corporate entrepreneurs say motivates them and the perceptions of their human resource manger.

Low‐threshold continuous laser operation (300–337 °K) of multilayer MO‐CVD AlxGa1−xAs‐GaAs quantum‐well heterostructures

Data are presented on multilayer AlxGa1−xAs‐GaAs quantum‐well heterostructures showing that cw 300–337 °K laser operation is possible at photoexcitation threshold levels (≲1.2×103 W/cm2, Jth≲500 A/cm2) comparable to better LPE double heterojunctions and much lower than all previous single or multiple quantum‐well heterostructures. These quantum‐well heterostructures are grown by metalorganic chemical vapor deposition (MO‐CVD) and consist of four 80–90‐A GaAs active layers coupled by three 80–90‐A AlxGa1−xAs (x∼0.35) barriers, all of which are sandwiched between 1‐ and 0.3‐μm AlxGa1−xAs (x∼0.40) confining layers.

Confined‐carrier luminescence of a thin In1−xGaxP1−zAsz well (x∼0.13, z∼0.29, ∼400 Å) in an InP p‐n junction

A thin (∼400 A) LPE In1−xGaxP1−zAsz ’’trap’’ on the p‐type side of an InP junction [Eg(InP)−Eg(InGaPAs) ≡ΔE∼245 meV], is filled by injection to a high enough density to make it possible to observe confined‐particle states and laser modes in a 70‐meV (≳600 A) range. The position of the modes is in good agreement with the transition energies expected for a finite potential well.

Multistage, monolithic ceramic microdischarge device having an active length of ∼0.27 mm

A three-stage, multilayer ceramic microdischarge device, having an active length of ∼267 μm and a cylindrical discharge channel 140–150 μm in diameter, has been developed and operated continuously in Ne gas. Stable glow discharges are produced for pressures above 1 atm, operating voltages as low as 137 V (at 800 Torr), and specific power loadings of ∼40 kW cm−3. The V–I characteristics for a fired ceramic structure exhibit a negative resistance, whereas the resistance is positive prior to firing. The manufacturability of the fabrication process as well as the “flow-through” and multistage design of this device make it well suited for the excitation of gas microlasers or the dissociation of toxic or environmentally hazardous gases and vapors.