Shimon Cohen

A peeling algorithm for extraction of the HBT small-signal equivalent circuit

Direct extraction is the most accurate method for the determination of equivalent-circuits of heterojunction bipolar transistors (HBTs). The method is based on first determining the parasitic elements and then the intrinsic elements analytically. The accuracy and robustness of the whole algorithm therefore is determined by the quality of the extraction of the extrinsic elements. This paper focuses on a new extraction method for the extrinsic capacitances which have proven to be the main source of uncertainty compared to the other extrinsic parameters. Concerning the intrinsic parameters, all the elements are extracted using exact closed-form equations, including exact expressions for the base-collector capacitances, which model the distributed nature of the base. The expressions for the base-collector capacitances are valid for both the hybrid-/spl pi/ and the physics-based T-topology equivalent circuits. Extraction results for InP HBT devices on measured S-parameters up to 100 GHz demonstrate good modeling accuracy.

An integrated heterojunction bipolar transistor cascode opto-electronic mixer

An integrated electrically pumped opto-electronic mixer consisting of two InP-GaInAs heterojunction bipolar transistors in a cascode configuration is demonstrated. Intrinsic down-conversion gains of 18.2 and 8.9 dB at RF optical modulation frequencies of 3 and 9.5 GHz were obtained. The performance of the cascode mixer and a single heterojunction bipolar transistor (HBT) opto-electronic mixer are compared. The performance of the cascode mixer was superior to the single HBT mixer, mainly at high frequencies. Up and down mixing conversion gains were measured and found comparable. A simulation was carried out by solving the nonlinear differential equations that correspond to the large-signal equivalent circuit. The results of the simulation enabled us to identify the principal nonlinear components in the equivalent circuit.

Control of morphology and crystal purity of InP nanowires by variation of phosphine flux during selective area MOMBE

We present experimental results showing how the growth rate, morphology and crystal structure of Au-catalyzed InP nanowires (NWs) fabricated by selective area metal organic molecular beam epitaxy can be tuned by the growth parameters: temperature and phosphine flux. The InP NWs with 20-65 nm diameters are grown at temperatures of 420 and 480 °C with the PH3 flow varying from 1 to 9 sccm. The NW tapering is suppressed at a higher temperature, while pure wurtzite crystal structure is preferred at higher phosphine flows. Therefore, by combining high temperature and high phosphine flux, we are able to fabricate non-tapered and stacking fault-free InP NWs with the quality that other methods rarely achieve. We also develop a model for NW growth and crystal structure which explains fairly well the observed experimental tendencies.

Resistive Switching in

Resistive switching in thin HfO2 films is studied using a metal-insulator-semiconductor bipolar transistor structure. Using this structure, electron injection into the semiconductor valence band can be distinguished from injection into the conduction band. In addition, the p-n junction serves as a sensitive detector of damage induced by the switching effect. The implications of the obtained experimental results on the validity of various conduction mechanisms through the insulator are discussed.

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A heterojunction bipolar transistor (HBT) optoelectronic mixer was studied experimentally and theoretically. A detailed large signal /spl pi/-model and a small signal analysis are described. The frequency dependence of down and up conversion has been analyzed and measured. In terms of conversion gain, the advantage of the down conversion process is clearly demonstrated. The values of parameters employed in the mixing process are also discussed for both large and small signal regimes.

Probed by a Metal–Insulator–Semiconductor Bipolar Transistor

Indium phosphide nanowires were grown by metalorganic molecular beam epitaxy using the selective-area vapor-liquid-solid method. We show experimentally and theoretically that the size of the annular opening around the nanowire has a major impact on nanowire growth rate. In addition, we observed a considerable reduction of the growth rate in dense two-dimensional arrays, in agreement with a calculation of the shadowing of the scattered precursors. Due to the impact of these effects on growth, they should be considered during selective-area vapor-liquid-solid nanowire epitaxy.

HBT optoelectronic mixer at microwave frequencies: modeling and experimental characterization

Arrays of gold single-strip and double-strip nano-antennas, with resonance in the wavelength range of 1200-1600 nm, were fabricated on the top of InGaAs/InP multi quantum well structure. Photo-luminescence from the quantum-wells was measured and shown to be enhanced by a factor of up to 9, with maximum enhancement wavelength corresponding to the nano-antennas resonance. Emission enhancement is attributed to the coupling of emitting charge-carriers to the plasmonic nano-antennas, causing an estimated increase in the radiative recombination rate by a factor of ~25, thus making it dominant over non-radiative recombination. This effect will enable fast modulation of InP-based nano-emitters spontaneously emitting at telecom-wavelength.

Shadowing and mask opening effects during selective-area vapor?liquid?solid growth of InP nanowires by metalorganic molecular beam epitaxy

The minority carrier mobility in the base of an InP/GaInAs heterojunction bipolar transistor (HBT) is obtained by measuring the change in base current induced by a magnetic field applied perpendicular to the direction of the current flow. The obtained mobility is consistent with results of the zero‐field time of flight technique.

Light emission rate enhancement from InP MQW by plasmon nano-antenna arrays

We report on the performance of abrupt InP-GaInAs-InP double heterojunction bipolar transistors (DHBTs) with a thin heavily doped n-type InP layer at the base-collector interface. The energy barrier between the base and the collector was fully eliminated by a 4-nm-thick silicon doped layer with N/sub D/=3/spl times/10/sup 19/ cm/sup -3/. The obtained f/sub T/ and f/sub MAX/ values at a current density of 1 mA//spl mu/m/sup 2/ are comparable to the values reported for DHBTs with a grade layer between the base and the collector.

Measurement of the minority carrier mobility in the base of heterojunction bipolar transistors using a magnetotransport method

The temperature dependence of the current-voltage characteristics of Ni-InGaAs alloy Schottky contacts to n-In0.53Ga0.47As was measured. Nearly ideal plots with an ideality factor close to unity were obtained. The Arrhenius curve across the wide temperature range of 80–300 K was perfectly linear, yielding a barrier height of 0.239 ± 0.01 eV. This value is substantially larger than previously reported. Conventional metal based Schottky diodes did not exhibit an ideal Schottky behavior. The ideal Schottky diode characteristics are attributed to the lack of oxidation and contamination of the interface between Ni-InGaAs and InGaAs.