Demonstrated are 1060 nm microelectromechanical-systems-based tunable vertical-cavity surface-emitting lasers (MEMS-VCSELs) with a 100 nm continuous tuning range under repetitively scanned operation at rates beyond 500 kHz and a 90 nm continuous tuning range under static operation. These devices employ a thin strained InGaAs multiple quantum well active region integrated with a fully oxidised GaAs/AlxOy bottom mirror and a suspended dielectric top mirror. The devices are optically pumped via 850 nm light. These ultra-widely tunable lasers represent the first MEMS-VCSELs reported in this wavelength range, and are ideally suited for application in ophthalmic swept-source optical coherence tomography.
Microelectromechanical-systems-based vertical-cavity surface-emitting lasers (MEMS-VCSELs) capable of a 150 nm continuous tuning range near 1310 nm are demonstrated. These devices employ a thin optically pumped active region structure with large free-spectral range, which promotes wide and continuous tuning. To achieve VCSEL emission at 1310 nm, a wide-gain-bandwidth indium phosphide-based multiple quantum well active region is combined with a wide-bandwidth fully oxidised GaAs-based mirror through wafer bonding, with tuning enabled by a suspended dielectric top mirror. These devices are capable of being scanned over the entire tuning range at frequencies up to 500 kHz, making them ideal for applications such as swept source optical coherence tomography and high-speed transient spectroscopy.
A voltage current convertor is described having a quasi complementary class AB architecture that is particularly suited to implementation using discrete power MOSFETs. High-voltage mirror designs are presented, enabling the construction of sources with kilovolt compliance range, tens of watts of output power and greater than 100 kHz bandwidth. GΩ output impedance and distortion below 1% can be obtained with no trimming or transistor matching.
An explicit solution is given to a generic feedback design problem
arising in flow control. The problem, which incorporates higher order
dynamics and capacity constraints, captures important features of a
number of design problems for units whose purpose is to smooth out flow
rate fluctuations between interconnected devices
An open-loop power control technique that establishes a linear relationship between a d.c. control voltage and the average load voltage is described. The output voltage is insensitive to input a.c. line voltage fluctuations as well as variations in supply frequency. The control output is versatile enough to drive a semiconductor on/off switch or an s.c.r. bridge operating either as a rectifier or as an inverter.
A new algorithm for the construction of (0, 1)-code matrices based
on the Greedy algorithm is proposed which allows the generation of code
matrices with any desired matrix dimension and weight. Such codes are
very useful in incoherent optical code-division multiple-access (CDMA)
systems combining wavelength hopping and time spreading. So it is
possible to achieve an auto-correlation function with zero sidelobes and
an aperiodic cross-correlation function with a maximum value of
Superluminescent AlGaAs-GaAs diodes with 15 mW output power and 1% Fabry-Perot modulation depth and modules with 3 mW polarisation maintaining fibre output have been developed. At output powers of more than 8 mW the effect of saturation on power fluctuations was observed.
An area- and power-efficient analogue adaptive equaliser (AEQ) is realised in a 0.13 m CMOS technology. The negative capacitance circuits are exploited at the equalisation filter to achieve wider bandwidth and larger high-frequency boosting, instead of using passive inductors that lead to a large chip area. Measured results demonstrate the data rate of 10 Gbit/s for 20 and 34 inch FR4 traces as channels, while dissipating only 6 mW from a single 1.2 V supply. The chip core occupies an extremely small area of 50 times 130 m<sup>2</sup>. To the best of the authors' knowledge, this chip achieves the lowest power consumption and the smallest chip area among the recently reported AEQs.
Splices of single-mode fused silica fibre having strengths equivalent to that of the as-drawn fibre of ˜800 ksi (5.5 GPa) with a coefficient of variation v of ≪0.01 are produced by fusion splicing with an H<sub>2</sub>-Cl<sub>2</sub>-O<sub>2</sub> flame. These results demonstrate that fused silica fibre can be reheated to fusion temperatures and retain original high strength. The results are statistically analysed with respect to variations in breaking load, fibre and splice diameter, and relative humidity.
A 533 MHz programmable phase-locked loop is designed for DDR applications using a switched current filter and implicit phase detection. The use of switched current technology allows a fully integrated loop filter which is much smaller than equivalent integrated passive filters, as a result the circuit occupies only 0.012 mm<sup>2</sup> on a 0.12 m 1.2 V digital CMOS process.
We have realised an electronic device with the aim of improving the relative stability in voltage dV/V of an electrostatic generator (voltage 400 kV, current 4 mA). This stability rose to 2Ã—10Â¿6 (from 2Ã—10Â¿5 previously) within a frequency bandwidth of 0.03Â¿1000 Hz. This electronic device, placed between the earth of the high-voltage generator and the earth of the utilisation, is autonomous, i.e. it can be applied for all kinds of generators, of low, high or very high voltage, with currents up to about 100 mA. The gain in stability can only be fixed after knowing the real characteristics of the generator, which should be improved.
A low-biased Mach-Zehnder modulator, optical amplification, and a high-power photodetector are employed to achieve all-photonic link gain as high as 44 dB over a transmission length of 40 km. The link has a 3 dB bandwidth of 6.25 GHz and a 20 dB noise figure.
A simple single-stage variable gain amplifier that offers 86 dB of gain variation, consumes 1.4 mW, and occupies 0.07 mm<sup>2</sup> is introduced and shown to have the largest gain range, lowest power, and smallest chip size ever reported based on 0.18 mum CMOS technology. A new approximated exponential equation is proposed, which offers the largest dB-linear range compared to all previously-reported approximated equations
The authors have demonstrated a strained InGaAs multiquantum well
laser grown on an InAs<sub>0.08</sub>P<sub>0.92</sub> ternary substrate.
The epitaxial structure was grown using metal organic vapour phase
epitaxy (MOVPE). The InAsP wafers were characterised using room
temperature photoluminescence, X-ray diffraction and X-ray topography.
Pulsed power levels of 60 mW/facet at h=1.75 μm were measured at
T=250 K. A characteristic temperature of T<sub>0</sub>=46 K was observed
over a temperature range of 78-250 K
The authors examine the high-frequency performance of a sub-0.1 mu m gate InAlAs/InGaAs HEMT with a thin InAs layer inserted into the InGaAs channel. The transconductance is 2.1 S/mm and the current-gain cutoff frequency is 264 GHz using a 0.08 mu m-long gate.
The authors show that the profiles of gate grooves can be
effectively manoeuvered by the selection of surface metals of ohmic
electrodes. The Ni surface metal is advantageous over Pt, since the
recess etching is independent of materials and is more spatially
homogeneous. These different etching behaviours and resulting
gate-groove profiles are attributed to the existence of electrochemical
effects during recess etching
A vertical MOSFET with a channel length of 85 nm has been
fabricated by molecular beam epitaxy. Compared to previous work, the
electrical behaviour has been greatly improved, allowing the use of
standard simulation tools for analysing the I-V characteristics. From
experimental and theoretical results. We conclude that for vertical
MOSFETs. The useful minimum channel length is not limited by the
technological constraints but by the physical limits of the electrical
performance. The useful minimum channel length is estimated to be ~80 nm
AlSb/InAs HEMTs with a 0.1 μm gate length have been fabricated
with a thin InAs subchannel separated from the InAs channel by 30
Å of AlSb. As a result, these HEMTs exhibit improved charge
control and a higher current-gain cutoff frequency. The devices have a
microwave transconductance of 850 mS/mm and an f<sub>T</sub> of 180 GHz
at V<sub>DS</sub>=0.6 V. After subtracting the gate bonding pad
capacitance, an f<sub>T</sub> of 250 GHz was obtained
A W-band divide-by-3 frequency divider with wide bandwidth and low power dissipation is presented using harmonic injection-locking technique. A cascode FET is employed for a self-oscillating second-harmonic mixer which is injection-locked by third-harmonic input to obtain the division order of three. The fabricated frequency divider using 0.1 μm GaAs metamorphic HEMT technology shows superior performance such as large bandwidth of 6.1 GHz around 83.1 GHz (7.3%) under small DC power consumption of 12 mW.
Losses as low 0.65 dB cm-1 (3 Â¿m width) and 0.3 dB cm-1 (8 Â¿m width) have been measured (Â¿ = 1.15 Â¿m) in high-confinement (NA Â¿ 0.45) GaAs/GaAlAs optical waveguides grown by MOCVD. The FabryÂ¿Perot loss measurement technique used in deduced to be accurate to Â±0.1 dB cm-1. These are the lowest losses reported for gudies of high electro-optic merit in III-V materials.
An accurate RF method using a linear regression of high-frequency Z-parameter equations at zero gate voltage is developed to extract resistances and inductances of sub-0.1 μm MOSFETs. Good agreement between the measured and modelled S-parameters is observed up to 30 GHz, verifying the accuracy of the RF method.
AlGa/GaAs modulation-doped field-effect transistors (MODFETs) have
been fabricated with `T' cross-section 0.1 μm gates using
electron-beam lithography. A unity current gain cutoff frequency f
<sub>T</sub> of 113 GHz has been measured for a spike-doped MODFET
with a GaAs buffer. This is the highest measured f <sub>T</sub>
reported to date for FETs of any kind
A sensitivity analysis of 0.1 mu m MOSFETs to manufacturing fluctuations has been carried out. The analysis reveals that the electrical parameter sensitivity in deep submicrometre devices differs from the currently produced micrometre size devices, making a revision of the validity of conventional semiconductor manufacturing heuristics for future technology mandatory.
A ytterbium sensitised thulium-doped blue upconversion ZBLAN fibre
laser pumped at 1065 nm by a high power, diode pumped, double clad fibre
laser is demonstrated. With a pump power of 2.8 W at 1065 nm, a blue
output power of 106 mW at 482 nm is achieved
The state of the art for a planar doped pseudomorphic Al<sub>0.2
</sub>Ga<sub>0.8</sub>As/In<sub>0.2</sub>Ga<sub>0.8</sub>As HEMT with a
gate length of 0.1 μm is presented. The devices exhibit an extrinsic
and intrinsic transconductance of 1070 and 1510 mS/mm. Respectively, a
maximum current density of 550 mA/mm and a peak current gain cutoff
frequency of 220 GHz. These results are the highest ever reported for
HEMTs fabricated on GaAs substrates
We have successfully realised a 0.1 μm T-gate pseudomorphic (Al
<sub>0.2</sub>Ga<sub>0.8</sub>As/GaAs high electron mobility transistor
(PM-HEMT) grown on a GaAs substrate by gas source molecular beam epitaxy
(GSMBE). The electronic transfer and mobility of the (Al<sub>x</sub>Ga
<sub>0.8</sub>As structure as functions of the aluminium composition
have been studied. The ohmic contact has also been optimised. For a
single-side doped structure, the devices exhibit the best RF and DC
performances of the AlGaInP/InGaAs system with a current density of 430
mA/ mm and an extrinsic transconductance Gm of 550 mS/mm. The cutoff
frequencies have been determined to be Ft=100 GHz and Fmax=160 GHz at
Vds=1.5 V. These excellent performances clearly show the high-quality
material grown by GSMBE
An InP double hetero-junction bipolar transistor (DHBT) distributed power amplifier MMIC with 35 dB gain, 42 GHz bandwidth and 15 dBm output power is reported. This represents the highest power and largest gain reported over this bandwidth from a single chip HBT amplifier. A lumped preamplifier with a novel distributed output is used to obtain high gain and wide bandwidth at these power levels.
De-embedded high frequency (HF) noise parameters of Ge p-channel
modulation doped field effect transistors (MODFETs) on a
Si<sub>0.4</sub>Ge<sub>0.6</sub> virtual substrate have been determined
for the first time. The 0.1 × 100μm devices have a minimum
noise figure NF<sub>min</sub> = 0.3 dB (0.5dB) ± 0.2dB, a noise
resistance R<sub>n</sub> = 95 Ω (90 Ω) ± 5 Ω,
an optimum reflection coefficient Γ<sub>opt</sub> = 0.7 ∠
6° and an associated gain G<sub>ass</sub> = 14 dB (13 dB) at 1.2 GHz
(2.5 GHz), at a bias corresponding to the optimum unity current-gain
frequency f<sub>T</sub> = 55GHz and the maximum oscillation frequency f
<sub>MAX</sub> = 135GHz. Noise results are given in the 1.2-12GHz
frequency range and 20-160 mA/mm current range
Short channel effects are thoroughly investigated in sub-0.1 μm
N channel SOI-MOSFETs by using a two-dimensional numerical simulation.
Drain-induced barrier lowering and charge sharing effects are calculated
as a function of the main device parameters for gate lengths down to
0.05 μm. The impact of the silicon layer, the gate oxide and the
buried oxide thicknesses, as well as of the Si film doping, are shown
quaternary channel has been introduced into n<sup>+</sup>-InAlAs/InGaAs
HEMTs. By adding a small amount of Al to the InGaAs channel, the bandgap
can be enhanced, which provides a higher reversed gate-drain breakdown
voltage. In addition, the associated impact ionisation process can be
suppressed in these quaternary channels. These HEMTs have been
demonstrated with a very low output conductance (4 mS/mm for x=0.2) and
a much smaller gate leakage current than conventional InP-HEMTs
The authors report on RF results of p-type Ge channel modulation
doped field effect transistors (MODFETs) with a gate length of 1.0
μm. The structure was grown on a relaxed 4.9 μm thick
compositionally graded Si<sub>0.4</sub>Ge<sub>0.6</sub> buffer. The
devices exhibit DC transconductances up to 190 mS/mm and saturation
currents up to 190 mA/mm. Cutoff frequencies of f<sub>T</sub> 59 GHz and
f<sub>max</sub>=135 GHz have been obtained. The f<sub>max</sub> value
is, to the knowledge of the authors, the highest reported so far for
p-type Si-based devices
It is shown that a further performance improvement in MODFETs with
InAs-inserted channel structures can be achieved by properly designing
the subchannel layer that lies directly under the main channel of the
InAs layer. The use of an In<sub>0.30</sub>Ga<sub>0.70</sub>As layer
grown with tensile strain on the InP substrate contributes to better
accommodation of the 2D electron gas in the InAs layer. This translates
to a >10% increase in the maximum extrinsic transconductance and an
8% increase in the current gain cutoff frequency of a 0.1 μm device
We have developed a separated absorption and multiplication (SAM)
avalanche photodiode (APD) with the thinnest reported InAlAs
multiplication layer of 0.1 μm and achieved 18.8 V operation. With
high speed and a high GB product of 140 GHz. This makes it possible to
realise a compact 10 Gbit/s APD receiver
The AM and FM response of an erbium-doped fibre amplifier has been characterised for signal modulation frequencies in the range 130 MHz to 15 GHz. Both the amplifier gain and phase are found to be constant for both amplitude-modulated and frequency-modulated signals.
It is shown that the threshold-voltage uniformity of 0.1 μm
InAlAs/InGaAs-based modulation-doped field-effect transistors with
different numbers of gate fingers and different gate widths can be
improved when a thin cap-layer structure is employed. This improvement
is based on the reduction of the recess time. This reduction suppresses
the difference in etching that results from the different etching rates
caused by the different electrochemical effects that occur because of
the varied gate layouts
Cutoff frequencies are measured for sub-0.25 mu m-gate InAlAs/InGaAs/InP HEMTs fabricated with a novel T-gate process using ion-beam etching in conjunction with both electron-beam lithography and photolithography. The cutoff frequency of 200 GHz is demonstrated by 0.12 mu m-gate HEMT.
The realisation of a millimetre-wave rectangular waveguide
fabricated using traditional monolithic technology is presented. The
rectangular waveguide has a cutoff frequency of 100 GHz and an operating
frequency of 105 GHz. The measured performance clearly shows that the
dominant TE<sub>10</sub> mode of propagation is supported
Results are reported of high-transconductance p-channel MODFETs
fabricated on Ge/Si<sub>0.4</sub>Ge<sub>0.6</sub> strained-layer
heterostructures grown by UHV-CVD. Devices with 0.1 mm gate length were
fabricated on compressively-strained pure-Ge channels with a Hall
mobility of 1750 cm<sup>2</sup>/Vs (30900 cm<sup>2</sup>/Vs) at room
temperature (T=77 K). These devices displayed room-temperature peak
extrinsic transconductances as high as 317 mS/mm, at V<sub>ds</sub>=-0.6
V, while the output conductance under the same bias conditions was only
18 mS/mm, corresponding to a maximum voltage gain of 18. At T=77 K, peak
extrinsic transconductances as high as 622 mS/mm were obtained at bias
voltages as low as V<sub>ds</sub>=-0.2 V. To our knowledge, the 77 K
transconductance is the highest ever reported for a p-type field effect
0.1 μm Ga<sub>0.51</sub>In<sub>0.49</sub>P/In<sub>0.2</sub>Ga
<sub>0.8</sub>As/GaAs PHEMTs grown by GSMBE have been realised. A new
interface GaInP/InGaAs has been studied and optimised to give a 2-DEG
density of 2×10<sup>12</sup> cm<sup>-2</sup> with a mobility of
5500 cm<sup>2</sup>/Vs at 300 K. The AuGe/Ni/Au ohmic contact has been
also optimised (R<sub>c</sub>=0.08 Ω mm) and a new nonselective
wet chemical etching technique based on iodic acid (HIO<sub>3</sub>) has
been developed. This device with single δ-doping exhibits state of
the art DC and RF performances in this new system with a current density
of 780 mA/mm, a breakdown voltage of 9 V a G<sub>m</sub> of 700 mS/mm
and an F<sub>t</sub> of 120 GHz
</sub>As HEMT structures were grown by molecular beam epitaxy (MBE) on
GaAs substrates. An inverse step metamorphic buffer (IS) was used to
reach a relaxation rate close to 98% and a mean cross-hatch of 2 nm.
This structure, which has a gate length of 0.1 μm, exhibits a peak
transconductance of 750 mS/mm and a current density of 650 mA/mm. A
current gain cutoff frequency F<sub>t</sub> of 160 GHz and a maximum
oscillation frequency F<sub>max</sub> of 400 GHz were also obtained.
These results clearly demonstrate the good electron transport properties
due to the high relaxation rate and the good filtering of dislocations
A new RF method based on the accurate extraction of the intrinsic transconductance and gate-source channel capacitance from measured S-parameters is proposed to determine the intrinsic cutoff frequency of sub-0.1 mu m MOSFETs. Using the RF technique, the intrinsic cutoff frequency enhancement with the linear dependence on I/L-poly(2) is observed in sub-0.1 mu m bulk n-MOSFETs. It is also observed that the reduction of extrinsic charging time is the most important to increase the measured cutoff frequency in sub-0.1 pal CMOS devices.
The authors report an all solid state, VLSI compatible,
electroluminescent device based on porous silicon with an external
quantum efficiency greater than 0.1%, under CW operation. The emission,
which is broadband and peaks at 600 nm, is detected above a low
threshold current density and voltage of 0.01 Am<sup>-2</sup> and 2.3 V,
Experimental results are reported for a coolerless wavelength division multiplex (WDM) source. Simple quadratic trends extracted from the laser tuning characteristics are used to stabilise the wavelength for 32, 100 GHz-spaced, channels. Wavelength accuracy of <0.1 nm was maintained over a temperature range of up to 50degC, limited by the lasers used in this work
The authors present the results of device modelling and circuit
simulation of recently reported sub-0.1 μm nMOSFET devices and obtain
excellent agreement with experimental data both at 300 K and at
cryogenic temperatures. The approach accurately describes the
subthreshold regime, short channel effects, and the notoriously
difficult knee region of the characteristics, making the model suitable
for deep submicrometre integrated circuit simulation
Maximum oscillation frequency f<sub>MAX</sub> as high as 188 GHz at 300 K and 227 GHz at 50 K are reported for a 0.1×30 μm<sup>2</sup> n-type strained Si/Si<sub>0.6</sub>Ge<sub>0.4</sub> modulation doped field-effect transistor (n-MODFET) together with high quality DC characteristics. These f<sub>MAX</sub> are the highest values reported so far for Si-based hetero-FETs. The frequency performances are discussed using analytical expressions of f<sub>MAX</sub> and f<sub>Ti</sub> (intrinsic current gain cutoff frequency) together with the main equivalent circuit elements extracted.
A serially concatenated code is presented which exhibits a turbo
cliff at 0.28 dB. The concatenation consists of an outer rate one-half
repetition code and an inner rate one recursive convolutional code. The
iterative decoding scheme was designed using the extrinsic information
transfer chart (EXIT chart)
A 10 GHz ring voltage controlled oscillator (VCO) has been designed and implemented in 0.12 μm CMOS technology. A source capacitively coupled current amplifier (SC3A) is adopted to realise this VCO. It can operate from 8.4 GHz up to 10.6 GHz with a phase noise of about -85 dBc/Hz at 1 MHz frequency offset. With the 1.5 V supply voltage, the current consumption is about 35 mA.
A comparator, fabricated in a 1.5 V/0.12 mum CMOS process, is presented. The commonly separated reset and active-load transistors of typical comparators are combined. In the input part two NMOS transistors are added to reduce power consumption. At a supply voltage of 0.5 V the comparator works at a maximal clock of 600 MHz and consumes 18 muW