Search

A novel concept for improving gamma ray spectroscopy in compact instruments is presented. The dual-range photon detector (DRPD) consists of a silicon drift detector (SDD) which is optically coupled with a La[Br.sup.3]([Ce.sup.3+]) crystal. In contrast to similar configurations investigated so far the SDD points to the radiation source. Pulse shape discrimination allows separating the distinct detection mechanisms which correspond to gamma absorption in the SDD or in the scintillator, respectively. This arrangement combines for the first time the excellent performance of an SDD as X-ray detector on its own with the striking energy resolution of a La[Br.sub.3] ([Ce.sup.3+]) scintillator read out by an SDD. The concept was successfully demonstrated with two experimental SDD-La[Br.sub.3]([Ce.sup.3+]) systems. An energy resolution (FWHM) of 2.7% and 2.9% at 662 keV was measured with the two distinct systems operated in scintillator mode whereas scintillator-photomultiplier combinations with the same crystals yielded only 3.3% and 3.1%, respectively. The SDD mode provided an energy resolution surpassing the scintillator resolution by about one order of magnitude in the limited energy range up to 100 keV. Measurements with various radioactive sources demonstrated that this mode uncovers line structures which could never be resolved with scintillators or CZT detectors. Homeland security programs could profit from the proposed detector concept. Index Terms--Energy resolution, gamma-ray spectroscopy, homeland security, pulse shape discrimination, radioisotope identification, scintillation detectors, silicon detectors.

In this paper, standard-cell Schottky rectifiers along with silicon-based merged p-i-n-Schottky (MPS) and p-i-n diodes, which are realized using a super junction technology, have been analyzed and compared by conducting extensive device and mixed-mode simulations through a 2-D finite-element grid. The main issues that concern these devices, such as the forward voltage drop, the leakage characteristic, and the reverse recovery, are treated, and the superior performances exhibited by the MPS rectifier with respect to the p-i-n diodes are experimentally validated. First, the basics on the used technology are reported by focusing on the high voltage capability of the new devices along with the low forward voltage drop during the ON-state conduction. The reverse-recovery behavior belonging to the MPS diode has been analyzed by exploring through several simulations the internal plasma dynamics. 2-D simulations of the turn-on behavior relative to the Schottky, p-i-n, and MPS rectifiers have been carried out in order to analyze the effects of the voltage overshoot phenomenon eventually occurring in the three diode structures. Index Terms--Merged p-i-n--Schottky (MPS) diode, physics-based model, p-i-n diode, Schottky diode, super junction device.

We have fabricated a position sensitive radiation detector by creating radiation damage regions in a Si photodiode. Radiation damage was created in layers at a depth of several [micro]m by [sup.7]Li and [sup.16]O ion beams which had an energy between 2 and 4 MeV. Ions were focused and scanned using a nuclear microprobe facility. The ion beam induced charge (IBIC) signals created in diodes during irradiation were simultaneously measured to monitor the exact ion beam fluence and analyzed to estimate the amount of defects created. By controlling the ion microbeam scanning system, graduated and position dependent radiation damage was produced in different micro-patterns. Such structures may be used as a simple position sensitive radiation sensor. Index Terms--Ion beam applications, photodiodes, position measurement, radiation detectors.

In this Paper we describe the performance of a radhard diode (AI/p+/n/n+/Al), developed in the framework of research and development programs for the future CMS experiment at LHC, for detection and spectrometry of X-and ')'-rays envisaging its use in characterization of porous structures by X-ray tomography. The diode's response was studied using [sup.57]Co, [sup.133]Ba, and [.sup.241]Am radioactive sources at room temperature. A reasonable good energy resolution was obtained in the energy range between 30 and 360 keV (FWHM = 5.2 keV and 5.7 keV, respectively). In the same energy range, measurements of full-energy peak efficiencies were carried out and compared with the theoretical values. For 59.5 keV photons the angular dependence of the efficiency was also measured. The results have demonstrated that this diode is appropriate for direct detection of low energy electromagnetic radiation. Index Terms--Microtomography, rad-hard silicon detectors, X-ray spectrometry.

This paper reports on the electrical characterization of the first prototypes of Geiger-Mode Avalanche Photodiodes (GM-APDs) and Silicon Photomultipliers (SiPMs) produced at ITC-irst, Trento. Both static and functional measurements have been performed in dark condition. The static tests, consisting in reverse and forward IV measurements, have been performed on 20 GM-APDs and 90 SiPMs. The breakdown voltage, the quenching resistance value and the current level have been proved to be very uniform. On the other hand, the analysis of the dark signals allowed the extraction of important properties such as the dark count rate, the gain, the after-pulse and optical cross-talk (in case of the SiPMs) rates. These parameters have been evaluated as a function of the bias voltage, showing trends perfectly compatible with the theory of the device. Index Terms--Geiger-mode avalanche photodiode, photodetectors, silicon photomultiplier.

As part of a program to investigate the feasibility of proton computed tomography, the most likely path (MLP) of protons inside an absorber was measured in a beam experiment using a silicon strip detector set-up with high position and angular resolution. The locations of 200 MeV protons were measured at three different absorber depth of PolyMethylMethAcrylate-PMMA (3.75, 6.25 and 12.5 cm) and binned in terms of the displacement and the exit angle measured behind the absorber. The observed position distributions were compared to theoretical predictions showing that the location of the protons can be predicted with an accuracy of better than 0.5 mm. Index Terms--Position Sensitive Particle Detectors, proton beams, silicon radiation detectors, tomography.

Effects of displacement and ionization damage on the impulse response of a high-bandwidth low breakdown voltage Si Avalanche Photodiode was investigated using a picosecond laser system. Damage was generated using either [Co.sup.60] [gamma]-irradiation or by scanning the device with an MeV ion microbeam. No shift in the impulse response characteristics and gain was observed for gamma doses as high as 100 kGy(Si). However, dark current measurements for irradiations with biases close to typical operating levels, exhibited enhanced ionization damage orders of magnitude higher than for no bias. Displacement damage introduced by the microbeam was used to differentiate between ionization damage in the guard ring isolation oxide and bulk damage. The absence of any marked change in the impulse response is discussed, as are possible mechanisms for the enhanced ionization damage.

The aim of this work is to validate experimentally the results of the Monte Carlo Recoil Energy Determination (MC-RED) nuclear physics code used to determine the deposited energy in a silicon volume taking into account the probabilistic approach of the physical phenomenon. A silicon sensor has been used to measure the deposited energy spectrum after an irradiation with a 14 MeV neutron source. Neutrons of 14 MeV were produced by the SAMES accelerator of the Valduc CEA research center. The experimental results were compared with the one obtained by the MC-RED code in the same silicon volume. To compare experiment and simulations, it requires that the complete neutron field be specified. We have to take into account the facility cell environment. Nuclear simulations were performed with the MCNP code to determine with accuracy the energy spectra of neutrons and gamma rays produced by this facility on the sensor. It is shown that the contribution of secondary neutrons is not negligible. Index Terms--Neutron-silicon interactions, neutron source, nuclear physics code, silicon detector, single event upset.

A framework is presented for understanding carrier generation and recombination mechanisms in irradiated silicon devices. Data obtained by many workers for irradiated bulk material and devices are analyzed and summarized, and key damage-factor dependences are identified. Measurements, simulations, and analyses support the conclusion that correlation of displacement damage effects with the rate of nonionizing energy loss (NIEL) for proton, neutron, pion, and heavy-ion bombardment is due to the dominant influence of defect subclusters. At low NIEL values (< 5 x [10.sup.-5] MeV-[cm.sup.2]/g),isolated defects dominate the electrical properties. At relatively high NIEL (>2 x [10.sup.-4] MeV-[cm.sup.2]/g), subclusters dominate. Enhanced carrier generation and recombination produced by those small disordered regions is considered. Modeling results are presented for behavior observed in the transition region between domination by isolated defects and by clusters. The model presented in this paper simultaneously accommodates defect cluster models and NIEL scaling phenomena in the same framework. Index Terms--Clusters, defects, displacement damage, NIEL, radiation effects, silicon.

It was demonstrated that Silicon Carbide Schottky Barrier Diodes exhibited anomalous charge collection with heavy ion irradiation. Consequently, the permanent damage and Single-Event Burnout was observed in spite of no known current sustaining mechanism. A model for the mechanism was proposed based on the device simulation. Index Terms--Heavy ion, Schottky barrier diode, silicon carbide, single-event burnout.

In this paper, the authors propose a gamma-ray spectrometer based on a La[Br.sub.3] :Ce scintillator coupled to a silicon drift detector (SDD). The SDD is a photodetector characterized by a very low noise thanks to the low value of output capacitance independent from the active area. With respect to a PMT, the SDD offers a higher quantum efficiency which reduces the spread associated to the statistic of photoelectrons generation. Also with respect to an APD, the SDD offers a lower photoelectrons statistic contribution, which, in the APD, is worsened by the excess noise factor with respect to pure Poisson statistics. Moreover, the SDD has a stable behavior, less sensitive to temperature and bias drift. In the past years, good energy resolutions were measured using a SDD coupled to a CsI:TI crystal. However, the long shaping time, to be used with this scintillator to prevent ballistic deficit, was too far to exploit the best noise performances achievable with a SDD obtained at shaping times in the order of 1 [micro]s. On the contrary, this optimum shaping time is fully compatible with the short decay time of the La[Br.sub.3] :Ce crystal (about 25 ns). The results of the experimental characterization of the La[Br.sub.3] :Ce-SDD gamma-ray spectrometer are presented in this work and are compared with the performances achieved with the same crystal coupled to a PMT and to a CsI(TI) crystal coupled to the same SDD. The SDD has an active area of 30 [mm.sup.2]. Antireflective coatings have been implemented. Good energy resolutions were measured at room temperature, thanks to the low leakage current of the detector: 2.7% at the [sup.137]Cs 661.7 KeV line and 6.1% at the [sup.57]Co 122 KeV line. A resolution of 5.7% at 122 KeV line was measured at 0[degrees]C. Index Terms--Gamma-ray spectroscopy, La[Br.sub.3], silicon drift detectors.

The responsivity of two types of silicon photodiodes, the AXUV series and the SXUV series was measured using synchrotron and laboratory radiation sources. Depending on the wavelength, the responsivity increased with temperature which was also found to be consistent with the decrease in the silicon bandgap energy causing a decrease in the pair creation energy.

Radiation hardness is a critical design concern for present and future silicon detectors in high energy physics. Tracking systems at the CERN Large Hadron Collider (LHC) are expected to operate for ten years and to receive fast hadron fluences equivalent to [10.sup.15][cm.sup.2] 1-MeV neutrons. Recently, low temperature operating conditions have been suggested as a means of suppressing the negative effects of radiation damage on detector charge collection properties. To investigate this effect, simulations have been carried out using the ISE-TCAD DESSIS device simulator. The so-called 'three-level model' has been used. A comprehensive analysis of the influence of the [V.sub.2], [C.sub.i][O.sub.i] and [V.sub.2]O capture cross sections on the effective doping concentration ([N.sub.eff]) as a function of temperature and fluence has been carried out. The capture cross sections have been varied in the range [10.sup.-18] - [10.sup.-12] [cm.sup.2]. The simulated results are compared with charge collection spectra obtained with 1064-nm laser pulses on devices irradiated with 23-GeV protons as a function of detector bias voltage. To validate the model, a wide range of temperature and fluence has been studied using a one-dimensional (1-D) simplified structure. Thousands of simulation results have been cross checked with the experimental data. The data between 190 K (the lower limit for simulations due to computational difficulties) and 290 K are well reproduced for all of the fluences considered. We conclude that the three-level model can be successfully used to predict irradiated detector behavior down to a temperature of at least 190 K. Index Terms--Cryogenic temperatures, device simulation, particle physics, radiation damage effects.

Avalanche multiplication and impact ionization coefficients in In[subscript 0.53]Ga[subscript 0.47]As diodes and heterojunction bipolar transistors are examined and reported.

Oxygenated and standard (not oxygenated) silicon diodes processed by CNM and IRST have been irradiated by 27 MeV protons and compared with standard devices from ST Microelectronics. As expected, the leakage current density increase rate ([alpha]) and its annealing do not show any significant dependence on starting material, oxygenation and/or device processing. On the contrary, oxygenation improves the radiation hardness by decreasing the acceptor introduction rate ([beta]) and mitigating the depletion voltage ([V.sub.dep]) increase, with the [beta] parameter depending also on starting material and/or effects related to device processing for standard diodes. Finally, these results are included in a general review on the state of the art for silicon detector radiation hardening, confirming the good performance of the considered technologies. Index Terms--Diodes, neutron radiation effects, oxygenation, proton radiation effects, radiation detectors.

A procedure is proposed for correcting the intensity-dependent phase delay of a reverse-biased silicon avalanche photodiode (APD).

The avalanche breakdown with observation of luminescence is discussed. The characteristics of p-n junction fabricated by aluminum-ion (Al(super +)) or boron-ion (B(super+)) implantation and high-dose Al(super +) -implantation into 4H-SiC (0001) is investigated.

The effect of silicon avalanche diodes (SADs) on the behavior of fuses in low-voltage (LV) power networks is shown, as well as the effect of the fuses on the energy dissipation in the SADs. In order to achieve this, an existing model developed for medium-voltage fuses was adapted for LV fuses operating in the presence of SADs. An SAD model was also developed. Both models were validated by laboratory measurement. The effects of fault closing angle and fault level on SAD energy dissipation are shown, and a general method for determining the SAD energy rating for any given situation is derived. Index Terms--Coordination, current-limiting fuse, energy, low-voltage power networks, silicon avalanche diode, simulation.

We measure the response of silicon photodiodes to irradiation by [H.sup.+], [He.sup.+], [C.sup.+], [N.sup.+], [O.sup.+], [Ne.sup.+], and [Ar.sup.+] ions with energies up to 60 keV. The unique properties of these photodiodes, including an ultrathin Si[O.sub.2] dead layer and 100% internal carrier collection efficiency, allow direct measurement of the total energy lost to nuclear (nonionizing) and electronic (ionizing) energy loss processes, which are important for quantifying effects such as damage and charge deposition. When plotted as a function of E/m[Z.sup.1/2], where E, m, and Z are the incident ion energy, mass, and atomic number, respectively, the responsivity is found to follow a single curve that represents all ion species and energies used in this study. This enables rapid, accurate estimation of damage and charge deposition by an ion as a function of penetration depth in silicon. A comparison of the measurements with the stopping and range of ions in matter (SRIM) Monte Carlo simulation code shows that SRIM significantly overestimates the fraction of the incident energy lost to electronic stopping processes for E/m[Z.sup.1/2] < 2 keV/amu. Index Terms--Electronic energy loss, ion radiation, ionizing radiation, nuclear energy loss, photodiodes, radiation effects, silicon detectors.

Research describing the characteristics of submicron silicon diodes is presented. In particular the excess noise and avalanche multiplication properties are examined.

The feasibility of laser action in erbium-doped silicon devices was analyzed.

A theoretical study is presented showing that the reverse leakage current thermally generated at the cutting edge of type-inverted [p.sup.+]-n single-sided silicon microstrip detectors is limited. Such behavior is shown to be related to a self-limiting mechanism acting on the edge surface generation, which prevents the net generation rate of electron-hole pairs at the detector edge from exceeding a saturation value, as the local hole density approaches its equilibrium value. Index Terms - Numerical device simulation, radiation damage, silicon microstrip detectors.

Findings of a study showed that in high-resistivity silicon bulk generation lifetime and surface generation, velocity can not be measured with acceptable accuracy using a single gated diode unless the gate length is suitably tailored. The accuracy of the evaluation of bulk generation lifetime was limited by nonidealities and contributing extra components to the gated-diode current which were not accounted for in the standard extraction procedure.

A special optical experimental technique was used to measure the safer reverse recovery limit in 3.3-kV Si power diodes. The approach effectively eliminated the influence of the junction termination by optical generation of a laterally-localized carrier plasma. The turn-off failures observed in the measurements at two temperatures showed no temperature dependence and could not be reproduced in ordinary one-dimensional or two-dimensional device simulations. Inhomogenous current distribution in the simulations appeared as the current decay ceases due to impact ionization.

The dynamic reverse-breakdown properties of low-voltage (

The neutron response of Schottky diodes that have been fabricated using 4H-SiC material was investigated. Experimental results showed that neutron detection using SiC diodes is feasible without significant degradation in the energy resolution, noise characteristics or the neutron counting rate even after exposure to high neutron fluences. However, degradation in the charge collection efficiency due to neutron damage-induced defects prevented self-biased operation after exposures to extremely high neutron fluences. These observations suggest that SiC-based detectors are highly suitable for a wide range of radiation monitoring applications.

The direct current-measured reverse breakdown characteristics of low-voltage (

The transport mechanisms in n-type annealed amorphous Si(sub 1-x)Cx/p-type crystalline Si heterojunctions for three different concentrations are investigated. It is shown that diodes with low doping concentration are the best since the phosphorous slightly diffuses into the crystalline silicon. On the other hand, multitunneling capture emission dominates high doping concentrations. Increased base acceptor doping concentrations also lead to excess current and increased leakage reverse current.

A study was conducted to analyze low frequency noise in gated n+-p silicon diodes based on the trapping and detrapping of holes in defect centers. The HP 4275A multifrequency LCR meter was utilized to determine the gate capacitance as a function of gate-to-substrate voltage. Individual Lorentzians related with local noise sources were identified to examine the physical features of the bulk defects responsible for the noise. Results indicated that thermal pretreatments lowered the defect density in the active area of diodes.

This paper presents the first silicon-flow sensor based on lift force. The sensor is a bulk-micromachined airfoil structure that uses the lift force as a sensing principle. The lift force acts normal to the flow in contrast to drag-force sensor types, where the force acts in the flow direction. The sensor utilizes the special distribution of the lift force along the length of the sensor structure. Since the sensor, like an airfoil, is mounted at a small angle to the flow, it induces very little flow disturbance. The sensor consists of two plates connected to a center beam. Each plate is 5 x 5-mm square with a thickness of 30 [[micro]meter]. The flow-induced forces deflect the two plates in the same direction, but with different magnitude. The deflections are detected by polysilicon strain gauges. The differential mode bridge makes the sensor insensitive to common mode deflection, e.g., acceleration forces. The lift-force principle is characterized using fundamental airfoil theory. The sensor has been experimentally verified, and a flow sensitivity of 7.4 [micro]V/V/[(m/s).sup.2] has been measured in both flow directions. Index Terms - Gas-flow sensor, lift force, piezoresistive.

The examination of forward-biased platinum (Pt)-doped (111) silicon p-n junction diodes with a linearly graded junction resulted in the identification of two electrically detected magnetic resonance (EDMR) signals at room temperature. Two peaks were observed from deep level transient spectroscopy analysis. It was therefore concluded that the two Pt trap levels are related to the two EDMR signals.

Successful development of a beta-sensitive intraoperative probe requires that the device be capable of selectively rejecting or reducing signals from background sources of photons. To address this problem we have designed and tested a unique stacked, dual solid-state detector probe. The first ion-implanted-semiconductor wafer detects a combination of beta particles and background photons, and the second wafer detects just the photon flux, due to the beta shielding effects of the first wafer. Using the data acquired from a positron-emitting source (18F), four methods of photon correction were tested. The scheme which incorporated a weighted subtraction of the data from the photon monitoring detector from the front detector was found to optimize performance. Sensitivity to beta particles was 4121.0 [+ or -] 52.3 cps/[mu]Ci, and the selectivity index was 0.99. Monte Carlo simulations revealed that these values are close to the theoretically optimal values possible, given the probe and source geometries. Additionally, a simulated tumor search utilizing an anthropomorphic torso phantom demonstrated the excellent potential of this device to intraoperatively localize sources of radiotracer-avid disease, such as malignant tumors. In summary, a dual, stacked ion-implanted-silicon detector beta-sensitive probe system has been developed and successfully tested. Index Terms - Beta probes, positrons, radiation detectors.

A double sided wedge microstrip silicon detector and a few simple pad [p.sup.+]n junctions, from the same silicon wafer, have been characterized and studied after 1 MeV neutron irradiation. The devices have been irradiated simultaneously at room temperature up to a fluence of 7.9 [10.sup.13] [cm.sup.-2]. A heating cycle has been performed after irradiation on the pad devices. Thermally Stimulated Currents measurements have been performed after each annealing step to study the radiation induced lattice disorder. Five deep traps with energy levels from 0.27eV to 0.44eV have been observed with trap concentrations in the range of [10.sup.12] to [10.sup.14] [cm.sup.-3]. The evolution of the lattice disorder as a function of the annealing time has been correlated with the changes in the electrical characteristics of the wedge detector.

Epitaxial grown thick layers ([greater than or equal to]100 [[micro]meter]) of high resistivity silicon (Epi-Si) have been investigated as a possible candidate for radiation hardened material for detectors in high-energy physics. As grown Epi-Si layers contain high concentrations (up to 2[multiplied by][10.sup.12] [cm.sup.-3]) of deep levels compared with that in standard high resistivity bulk Si. After irradiation of test diodes by protons ([E.sub.p] = 24 GeV) with a fluence of 1.5[multiplied by][10.sup.11] [cm.sup.-2], no additional radiation induced deep traps have been detected. A reasonable explanation is that there is a sink of primary radiation induced defects (interstitial and vacancies), possibly by as-grown defects, in epitaxial layers. The 'sinking' process, however, becomes non-effective at high radiation fluences ([10.sup.14] [cm.sup.-2]) due to saturation of epitaxial defects by high concentration of radiation induced ones. As a result, at neutron fluences of 1[multiplied by][10.sup.14][cm.sup.-2] the deep level spectrum corresponds to well-known spectrum of radiation induced defects in high resistivity bulk Si. The net effective concentration in the space charge region equals to 3[multiplied by][10.sup.-12] [cm.sup.-3] after 3 months of room temperature storage and reveals similar annealing behavior for epitaxial as compared to bulk silicon.

Silicon [p.sup.+]n junctions irradiated with neutron and proton fluences in the range 5x[10.sup.11]- 4x[10.sup.15] [cm.sup.-2] and non-irradiated SI LEC GaAs Schottky barriers have been analyzed. In silicon the concentration Nt of the main radiation-induced deep traps (Et [approximately equal to]0.44 - 0.54 eV) is found to increase as [N.sub.t] [Alpha] f achieving values up to 5x[10.sup.15] [cm.sup.-3] and a mobility saturation at 100[cm.sup.2]/Vs has been observed at the highest fluences. A quantitative comparison between heavily irradiated silicon and non-irradiated GaAs evidenced similar charge collection efficiencies, a quasi-intrinsic bulk and similar concentrations of deep defects. On this basis, a unique model, correlating the lattice disorder and the detector performance, is suggested.

We studied three different types of silicon sensors: PIN diodes, circular drift detectors, both made at the Delft University of Technology (DUT), and Hamamatsu S5345 avalanche photodiodes. Measurements have been carried out in the same optimized experimental setup, both at room temperature and at low temperatures. Comparison is made for direct X-ray detection and CsI(TI) scintillation light readout.

Large area (63.6 mm x 64 mm) n-on-n silicon strip detectors have been fabricated, implementing various p-stop structures in the n-side. The detectors were characterized in laboratory and in beamtests. The beamtests showed that the individual p-stop structure collected less charge in the region between the strips than other p-stop structures.

An x-ray spectrometer combining multi-element silicon detectors and multi-channel integrated circuit pulse-processing electronics is being developed for low noise, high count rate synchrotron x-ray fluorescence applications. This paper reports on the issues surrounding the use of highly segmented silicon detectors for x-ray spectroscopy. Several different detector geometries were modeled using commercially available device simulation software, and selected geometries were fabricated using planar processing techniques on high resistivity silicon. The detectors were characterized using a 5 [[micro]meter] diameter 8.5 keV x-ray beam, and 55Fe and 109Cd radioisotope sources. Spectral background, anomalous peaks, peak-to-background and charge sharing between adjacent detector elements were studied. The measured x-ray spectral responses are interpreted with respect to the device simulations. These measurements bring to light the effects of detector design, detector processing techniques and detector materials properties on the spectral response of the detector.

We have irradiated an n-side silicon microstrip detector to an equivalent high energy fluence of 1 x [10.sup.15] p [cm.sup.-2] using 55 MeV protons. We determined the median pulse height to be 0.7 fC at a bias voltage of 180 V, and deduced a depletion region of about 80 [[micro]meter].

We present a study that shows that charge collection efficiency in silicon microstrip detectors depends on the geometry of the p-stop used to isolate the strips on the Ohmic side. Detector signals for four kinds of p-stops were studied using a laser test stand. We propose an optimal p-stop geometry which realizes acceptable charge collection efficiency as well as low interstrip capacitance and low noise.

A study resolving two hits in a 45x45 mm rectangular n-type Silicon Drift Detector is presented as a function of drift field using a pulsed Nd:Yag laser. The data are analyzed under the assumption of the general form of a Gaussian distribution in two variables (including correlations). The two hit resolving power degrades with drift distance. As the two electron clouds approach each other their correlation coefficients are shown to increase and be anti-correlated. Arguments for optimal two hit resolution versus drift field are presented. A simple method to determine whether electron cloud distributions arise from multiple overlapping hits or single hits is demonstrated. Practical implications for analyzing data from high occupancy experiments such as STAR at the RHIC collider are discussed.

Silicon circuits, now penetrating well into the microwave frequency range, use lossy silicon substrates. Consequently, the microwave performance of transmission lines on this substrate becomes increasingly important and has been investigated here up to 20 GHz. It is shown that transmission lines on 20-[Omega] [center dot] cm substrates have no need for backside metallization and backside via holes. Two models for different line types are derived from measurements and verified against them. A coplanar waveguide (CPW) with an overall width of less than 30 [[micro]meter] was fabricated with an attenuation of 0.5 dB/mm at 20 GHz, which is acceptable for monolithic microwave integrated circuit (MMIC) design. Index Terms - Coplanar waveguides, microstrip, MMIC's, silicon, transmission lines.

A circularly polarized (CP) silicon-integrated W-band rectenna (rectifying antenna) for use in six-port polarimetric radar systems was designed, numerically optimized, and fabricated. A rigorous numerical optimization was performed by using the supergrid method (SGM). The rectenna applies a novel low-loss purely planar dual-patch antenna (DPA) layout, which allows the receiver to be manufactured using monolithic integration. The measurement results for the receiver demonstrate an excellent cross-polarization discrimination (XPD) >14 dB @ 76 GHz over a wide range of the scan angle (12 dB @ [+ or -]20 [degrees]). Index Terms - Active antenna, automotive radar, circular polarization, circularly polarized antenna.

This paper presents three-dimensional (3-D) Si monolithic microwave integrated circuit (MMIC) technology and Si MMIC operation up to K-band using this technology, and describes X- and K-band mixers with design details and measurements. The 3-D Si MMIC technology isolates passive circuits from the low-resistivity Si substrate. The evaluations use Si bipolar transistors with an emitter size of 0.3 [[micro]meter] x 13.4 [[micro]meter] x 9 and [f.sub.max] of 30 GHz. The mixers are base and collector LO injection types. The mixers, fabricated in an area of 0.76 mm x 0.54 mm for the X-band mixers and in 0.46 mm x 0.42 mm for the K-band mixers, exhibit a frequency conversion loss of 5-12 dB from 3.5 to 10 GHz and from 10 to 25 GHz. This technology is extremely effective for single-chip integration of receivers and transmitters and also for mixed-mode MMIC's up to K-band frequencies. Index Terms - Bipolar transistor, masterslice, mixer, MMIC's, multilayer, silicon, three-dimensional structure.

This paper presents an extensive electrical characterization of Si/SiGe/Si heterojunction bipolar transistors (HBT's) grown by molecular beam epitaxy (MBE). These devices are designed for microwave and millimeter-wave applications since they present a maximum oscillation frequency in the 40-GHz range. The processing technology, featuring a high-quality oxide passivation, results in ideal Gummel plots and an input noise corner frequency of 250 Hz at lowest. A dielectric resonator oscillator (DRO) at 4.7 GHz has, therefore, been realized. The measured phase-noise level of this oscillator is below -135 dBc/Hz at 10kHz offset frequency, which is at least 10 dB better than the best FET or HBT state-of-the-art DRO's. Index Terms - Dielectric resonator oscillators, Ge-Si alloys, heterojunction bipolar transistors, low-frequency noise, microwave oscillators, noise, 1/f noise, phase noise, SiGe alloys, silicon.

We report on design aspects and the implementation of RF integrated circuits (RFIC's) using TEMIC's SiGe heterojunction bipolar transistor (HBT) technology. SiGe HBT's with 50-GHz [f.sub.T] and [f.sub.max] were obtained by a production process including polysilicon resistors, nitride capacitors, and spiral inductors showing Q values up to 10. RF noise figures down to 1 dB at 2 GHz with an associated gain of 14-dB and 1-kHz 1/f corner frequency were obtained. The differences between the device parameters of Si bipolar junction transistor (BJT) and SiGe HBT technology and their influence on IC design are discussed. Design and measurement results of RFIC's, including a low-noise amplifier (LNA) and a power amplifier (PA) for application in a 1.9-GHz digital enhanced cordless telecommunications (DECT) RF front-end and 900-MHz preamplifier for a global system for mobile communication (GSM) power module are presented. Index Terms - Amplifier noise, bipolar integrated circuits, mobile communications, power amplifiers, silicon-germanium.

We investigate the base-profile design issues associated with optimizing ultrahigh vacuum/chemical vapor deposition (UHV/CVD) silicon-germanium (SiGe) heterojuction bipolar transistors (HBT's) for minimum broad-band noise. Using the simulator for cryogenic research and SiGe bipolar device optimization (SCORPIO), the impact of Ge profile, base doping level, and base thickness on minimum noise figure (N[F.sub.min]) are quantitatively examined across the -55 [degrees] C-125 [degrees] C temperature range. We introduce a novel Ge profile for optimum N[F.sub.min], which allows independent control of current gain ([Beta]) and achieves maximum [f.sub.T] while maintaining thermodynamic stability. Simulations show that this profile can achieve a [Beta] of [approximately]200, a peak [f.sub.T] > 50 GHz, a peak [f.sub.max] > 60 GHz, and an N[F.sub.min] < 0.5 dB at 2 GHz and 70 GHz, and a peak [f.sub.max] > 90 GHz. These 300-K performance values improve as the temperature is reduced. Index Terms - Heterojunction bipolar transistors, germanium, semiconductor device modeling, semiconductor device noise, silicon.