Nicolas Zerounian

230-GHz self-aligned SiGeC HBT for optical and millimeter-wave applications

This paper describes a 230-GHz self-aligned SiGeC heterojunction bipolar transistor developed for a 90-nm BiCMOS technology. The technical choices such as the selective epitaxial growth of the base and the use of an arsenic-doped monocrystalline emitter are presented and discussed with respect to BiCMOS performance objectives and integration constraints. DC and high-frequency device performances at room and cryogenic temperatures are given. HICUM model agreement with the measurements is also discussed. Finally, building blocks with state-of-the-art performances for a CMOS compatible technology are presented: A ring oscillator with a minimum stage delay of 4.4 ps and a 40-GHz low-noise amplifier with a noise figure of 3.9 dB and an associated gain of 9.2 dB were fabricated.

Direct and indirect band gap room temperature electroluminescence of Ge diodes

Germanium is a promising material for electrically pumped light emitters integrated on silicon. In this work, we have investigated the room temperature electroluminescence of pure germanium diodes grown by metal organic chemical vapor deposition. The dependence of the optical response of the p-n diodes is studied as a function of the injected current. Both direct and indirect band gap recombinations are observed at room temperature around 1.6 and 1.8 μm. The amplitude of the direct band gap recombination is equivalent to the one of the indirect band gap.

Quality factor of Si-based photonic crystal L3 nanocavities probed with an internal source.

We have investigated the quality factors of silicon-based photonic crystal nanocavities using the photoluminescence of a single layer of Ge/Si self-assembled islands as an internal source. We focus on membrane-type L3 elongated cavities with or without their lateral edge air holes shifted in position. The photoluminescence measurements are performed at room temperature. We show that the quality factor of the fundamental mode observed at a normalized frequency u = a/lambda~_ 0.25 is strongly dependent on the incident pump power. This dependence is associated with the free-carrier absorption of the photogenerated carriers. The slope of the quality factor vs. incident pump power gives access to the carrier recombination dynamics in these Si-based nanocavities. The measurements indicate that the carrier dynamics is controlled by nonradiative recombination associated with surface recombinations. A surface recombination velocity of 4.8 x 10(4) cm/s is deduced from the experiments. The spectral red-shift of the cavity modes as a function of incident pump power is correlated to the temperature rise due to thermo-optic effects. The measured temperature rise, which can reach 190 K, is correlated to the value estimated by a thermal analysis.

230 GHz self-aligned SiGeC HBT for 90 nm BiCMOS technology

This paper describes a 230 GHz self-aligned SiGeC HBT featuring a selective epitaxial base and an arsenic-doped monocrystalline emitter. These technical choices are presented and discussed with respect to BiCMOS performance objectives and integration constraints.

Low temperature analysis of 0.25 /spl mu/m T-gate strained Si/Si/sub 0.55/Ge/sub 0.45/ n-MODFET's

A low temperature dc and HF investigation of 0.25 /spl mu/m T-gate Si/Si/sub 0.55/Ge/sub 0.45/ n-MODFETs is presented. Outstanding maximum oscillation frequencies f/sub max/ range from 100-120 GHz at 300 K up to 195 GHz at 50 K. These high-frequency characteristics are the first reported at low temperature on Si/SiGe n-MODFETs and are also the highest room temperature data reported so far; physical modeling is used to explain the main trends observed when cooling down the n-MODFET. Many experimental data are presented. The dependence on temperature and biases of the important small-signal equivalent circuit parameters is investigated to analyze the device high-frequency performances and the minimum noise figure of the intrinsic device is determined.

SiGe HBTs featuring f T ≫400GHz at room temperature

This paper presents the results of investigations on process thermal budget reduction in order to increase the operation frequency of SiGe HBTs. We describe the variations of DC and AC characteristics of the devices with the spike annealing temperature. Record peak fT values of 410 GHz and 640 GHz are reported at room and cryogenic temperatures respectively.

On the use of cryogenic measurements to investigate the potential of Si/SiGe:C HBTs for terahertz operation

The transit times analysis, at room and cryogenic temperatures, of SiGe HBTs featuring various ftau/fmax trade-offs is performed. It allows to identify the principal development axes to reach half-terahertz at 300 K, a frequency already obtained at 40 K.

Tensile-strained germanium microdisk electroluminescence

We report room temperature electroluminescence of tensile-strained germanium microdisks. The strain is transferred into the microdisks using silicon nitride stressors. Carrier injection is achieved with Schottky contacts on n-type doped germanium. We show that a biaxial tensile-strain up to 0.72% can be transferred by optimizing the carrier injection profile. The transferred strain is measured by the electroluminescence spectral red-shift and compared to finite element modeling. We discuss the impact of this strain level to achieve population inversion in germanium.

Circuit-tunable sub-wavelength THz resonators: hybridizing optical cavities and loop antennas.

We demonstrate subwavelength electromagnetic resonators operating in the THz spectral range, whose spectral properties and spatial/angular patterns can be engineered in a similar way to an electronic circuit. We discuss the device concept, and we experimentally study the tuning of the resonant frequency as a function of variable capacitances and inductances. We then elucidate the optical coupling properties. The radiation pattern, obtained by angle-resolved reflectance, reveals that the system mainly couples to the outside world via a magnetic dipolar interaction.

Schottky electroluminescent diodes with n-doped germanium

n-doped germanium can be used as an active material for the realization of an optical source under electrical pumping. We propose to use Schottky contacts for germanium electroluminescent devices, and we show that carrier injection and electroluminescence in these Schottky devices can be optimized by depositing a thin Al2O3 interfacial layer on top of n-doped germanium. In the latter case, hole injection is optimized due to the drastic decrease of interface trap densities and room-temperature electroluminescence can be observed at small current injection with a higher differential efficiency as compared to the standard Schottky sample.