F.G. Della Corte

Temperature dependence of the thermo-optic coefficient in crystalline silicon between room temperature and 550 K at the wavelength of 1523 nm

The temperature dependence of the thermo-optic coefficient for crystalline silicon has been measured in the temperature range between room temperature and 550 K at the wavelength of 1523 nm by means of an interferometric technique. This technique, which requires a very simple experimental setup, is based on the observation of the fringe pattern produced by temperature changes in a Fabry–Perot resonator. Measurement results indicate that the thermo-optic coefficient is independent on the sample doping and crystal plane orientation. The experimental data appear to be in agreement with the few values reported to date at this important wavelength. The temperature dependence of the excitonic band gap is also calculated by fitting these data with a recently introduced model of ∂n/∂T.

Amorphous silicon-based guided-wave passive and active devices for silicon integrated optoelectronics

Waveguides and interferometric light amplitude modulators for application at the 1.3- and 1.55-/spl mu/m fiber communication wavelengths have been fabricated with thin-film hydrogenated amorphous silicon and its related alloys. The technique adopted for the thin-film growth is the plasma- enhanced chemical vapor deposition, which has been shown to give the lowest defect concentration in the film. Consequently the proposed waveguiding structures take advantage of the low optical absorption shown by a-Si:H at photon energies below the energy gap. In addition a good radiation confinement can be obtained thanks to the bandgap tailoring opportunity offered by this simple and inexpensive technology. In particular rib waveguides, based on a a-SiC:H/a-Si:H stack, have been realized on crystal silicon, showing low propagation losses. Recently, however, a new interest as low as 0.7 dB/cm. The same structure has been utilized for the fabrication of thermooptic Fabry-Perot modulators with switching times of 10 /spl mu/s. Modulators based on the alternative waveguiding configuration ZnO/a-Si:H, giving comparable results, are also presented.

A temperature all-silicon micro-sensor based on the thermo-optic effect

A new class of temperature silicon micro-sensors, based on an interferometric optical technique, is presented. The sensing element consists of a planar Fabry-Perot cavity defined on a silicon wafer by highly anisotropic reactive ion etching, and is therefore suitable for full integration with other standard opto- and micro-electronic devices. Preliminary temperature measurements have been performed with the temperature resolutions predicted by the theory. The limit performances, in terms of resolution, speed of operation and energy dissipation of this class of sensors are discussed in detail. In particular, a final temperature resolution of 0.064/spl deg/C is expected for a low loss interferometric cavity, with a settling time of 150 ns and a 0.2% readout error. An energy resolution as low as 30 nJ is also estimated.

An Analytical Model of the Forward I– V Characteristics of 4H-SiC p-i-n Diodes Valid for a Wide Range of Temperature and Current

The forward I-V characteristics of 4H-SiC p-i-n diodes are studied in a wide range of currents and temperatures by means of an analytical model that allows us to highlight the minority current contributions in various diode regions, namely, the highly doped regions, the neutral base, and the space charge layer. By accounting for the doping dependence of various physical parameters, such as bandgap narrowing, incomplete doping activation, carrier lifetime, and mobility, the model turns useful to investigate the role of various material properties at different current levels and temperatures. The accuracy of the model is verified by comparisons with numerical simulations and experimental data in a wide range of currents and temperatures, so that this model turns very useful for better understanding the impact of technological parameters on the steady-state behavior of diodes and obtaining an accurate circuital model of diodes.

Fast infrared light modulation in a-Si:H micro-devices for fiber-to-the-home applications

Abstract We have produced and measured the properties of a fast switching micro-optic device in a rib-like configuration working at the 1.3 and 1.55 μm fiber communication wavelengths for fiber-to-the-home applications. The core guiding layer is made of intrinsic hydrogenated amorphous silicon (a-Si:H) deposited by plasma enhanced chemical vapour deposition (PECVD) with absorption coefficients sufficiently small at the wavelength of interest. The signal modulation is performed exploiting the thermo-optic effect of thin film a-Si:H in a Fabry–Perot waveguide integrated interferometer. Switching times

Analytical model for GaAs pin diodes for a wide range of currents and temperatures

An analytical model is proposed which can describe the I-V characteristics of a GaAs pin diode in a wide range of currents from room temperature up to 220°C and above. Be+ implanted test diodes with low leakage current have been produced. Good agreement was found between experimental and theoretical I-V plots over the full range of currents and temperatures. It is shown for good-quality diodes which current components are dominant for different operating conditions.

Measurement of the thermo-optic coefficient of a-Si:H at the wavelength of 1500 nm from room temperature to 200 °C

Abstract The thermo-optic coefficient (TOC) of hydrogenated amorphous silicon (a-Si:H) has been measured in the temperature range 30–200 °C, at the communication wavelength of 1.55 μm . The experimental data have been fitted using a single oscillator model that takes into account the shape of e2-spectrum of the amorphous semiconductor. The extracted parameters significantly extend, and are consistent with, the few data reported in the literature. An interesting analogy with crystalline silicon (c-Si) is also found and discussed.

Electrooptical Modulating Device Based on a CMOS-Compatible

In this paper, we report results on a field-effect-induced light modulation at λ = 1.55 μm in a high-index-contrast waveguide based on a multisilicon-on-insulator platform. The device is realized with the hydrogenated amorphous silicon (α-Si:H) technology, and it is suitable for monolithic integration in a CMOS IC. The device exploits the free-carrier optical absorption electrically induced in the semiconductor core waveguide. The amorphous silicon waveguiding layer contains several thin dielectric films of amorphous silicon carbonitride (α-SiCN) embedded along its thickness, thus highly enhancing the absorbing action of the modulator held in the on state.

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Abstract Starting from an a-Si:H/a-SiC:H stack deposited by glow discharge on a crystal silicon wafer, we have fabricated and measured the properties of rib waveguides suitable for infrared optical communication purposes. Propagation losses as small as 0.7 dB/cm have been measured. The same waveguiding structure has been utilised for the construction of Fabry–Perot interferometers. As the process is compatible with the standard microelectronic technologies, the integration of optical and electronic functions on the same chip becomes possible.

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The forward J-V characteristics of 4H-SiC p-i-n diodes are investigated in a wide range of currents and temperatures by means of an analytical model which describes in detail the role of the various physical parameters, such as bandgap narrowing effect, incomplete doping activation and doping-dependent mobility. In order to analyze the influence of the SiC properties at different injection regimes, the total diode current is expressed in terms of the minority current contributions in the various device regions. The accuracy of the model is verified by comparisons with numerical simulations and experimental data reported in the literature. The analysis shows that the proposed model can turn useful for a better understanding of the device behavior and for implementation in circuit simulators.