Avalanche Multiplication Region Research Articles

A peak enhancement of frequency response of waveguide integrated silicon-based germanium avalanche photodetector

Avalanche photodetectors (APDs) featuring an avalanche multiplication region are vital for reaching high sensitivity and responsivity in optical transceivers. Waveguide-coupled Ge-on-Si separate absorption, charge, and multiplication (SACM) APDs are popular due to their straightforward fabrication process, low optical propagation loss, and high detection sensitivity in optical communications. This paper introduces a lateral SACM Ge-on-Si APD on a silicon-on-insulator (SOI) wafer, featuring a 10 μm-long, 0.5 μm-wide Ge layer at 1310 nm on a standard 8-inch silicon photonics platform. The dark current measures approximately 38.6 μA at −21 V, indicating a breakdown voltage greater than −21 V for the device. The APDs exhibit a unit-gain responsivity of 0.5 A/W at −10 V. At −15 V, their responsivity reaches 2.98 and 2.91 A/W with input powers of −10 and −25 dBm, respectively. The device's 3-dB bandwidth is 15 GHz with an input power of −15 dBm and a gain is 11.68. Experimental results show a peak in impedance at high bias voltages, attributed to inductor and capacitor (LC) circuit resonance, enhancing frequency response. Furthermore, 20 Gbps eye diagrams at −21 V and −9 dBm input power reveal signal to noise ratio (SNRs) of 5.30. This lateral SACM APD, compatible with the stand complementary metal oxide semiconductor (CMOS) process, shows that utilizing the peaking effect at low optical power increases bandwidth.

Single-photon avalanche diode fabricated in standard 55 nm bipolar-CMOS-DMOS technology with sub-20 V breakdown voltage.

This paper presents a single-photon avalanche diode (SPAD) in 55 nm bipolar-CMOS-DMOS (BCD) technology. In order to realize a SPAD having sub-20 V breakdown voltage for mobile applications while preventing high tunneling noise, a high-voltage N-well available in BCD is utilized to implement the avalanche multiplication region. The resulting SPAD has a breakdown voltage of 18.4 V while achieving an excellent dark count rate of 4.4 cps/µm2 at the excess bias voltage of 7 V in spite of the advanced technology node. At the same time, the device achieves a high peak photon detection probability (PDP) of 70.1% at 450 nm thanks to the high and uniform E-field. Its PDP values at 850 and 940 nm, wavelengths of interest for 3D ranging applications reach 7.2 and 3.1%, respectively, with the use of deep N-well. The timing jitter of the SPAD, full width at half maximum (FWHM), is 91 ps at 850 nm. It is expected that the presented SPAD enables cost-effective time-of-flight and LiDAR sensors with the advanced standard technology for many mobile applications.

Performance of proportional counters filled with Xe + 5% TMA under high count rate-pressure scaling

The total space charge effect includes the cumulative effect of positive ions created from many different avalanches. The presence of positive ions in the avalanche multiplication region reduces the gas amplification factor. The gas gain has been measured for a low and high count rate by means of the current method for sealed cylindrical proportional counters of radius b = 12.5 mm with an axially placed anode of radius a = 50 μm. The gas gain curves covered the whole gas gain region from the ionisation chamber to that close to continuous discharge. The gas gain was determined for 5,9 keV X-rays of varying intensity and of constant high radiation intensity. For any count rate there is always a critical voltage, which divides the operation range of the counter into two regions, i.e. the region in which no changes in the gas gain with a count rate are observed and the region in which the space charge of positive ions reduces the gas gain. The values of current over which a 5% reduction in gas gain is observed have been determined. The measurements were made for a mixture pressure range from 294 hPa to 1800 hPa. The obtained results, which are presented here, can be favourable for micromegas-TPC operating in an Xe-TMA mixture.

Impact ionisation in Al0.9Ga0.1As0.08Sb0.92 for Sb-based avalanche photodiodes

We report the impact ionisation coefficients of the quaternary alloy Al0.9Ga0.1As0.08Sb0.92 lattice matched to GaSb substrates within the field range of 150 to 550 kV cm−1 using p-i-n and n-i-p diodes of various intrinsic thicknesses. The coefficients were found with an evolutionary fitting algorithm using a non-local recurrence based multiplication model and a variable electric field profile. These coefficients indicate that an avalanche photodiode not only can be designed to be a function in the mid-wave infrared but also can be operated at lower voltages. This is due to the high magnitude of the impact ionisation coefficients at relatively low fields compared to other III–V materials typically used in avalanche multiplication regions.

Proposal of a quantum ring intersubband photodetector integrated with avalanche multiplication region for high performance detection of far infrared

In this paper, a novel design of quantum ring infrared photodetector (QRIP) is proposed based on an additional avalanche multiplication region and its performance theoretically is investigated. The device consists of two intrinsic regions including: (i) quantum ring based absorption region which is responsible for absorption longer wavelength radiations and (ii) avalanche multiplication region for multiplying the generated carriers in absorption layer. Since lower electric fields are needed for absorption region to keep the dark current low and higher fields are required for multiplication region, a highly doped charge layer is used to separate absorption and multiplication regions and non-uniformly distribute the electric field. Also to further reduction of dark current, resonant tunneling barriers are embedded in absorption region to provide only a pass for optically excited electrons. Simulation results shows a higher responsivity and specific detectivity about 40A/W and 2×1010cmHz1/2/W at λ=20μm, respectively.

Quantum-dot-based single-photon avalanche detector for mid-infrared applications

A single-photon detector is presented with quantum dot (QD) layers in its absorption region. The proposed detector is a three-terminal device in which a QD-based absorption region is integrated with an avalanche multiplication region through a tunneling barrier and the applied bias of each region can be controlled separately. The mid-infrared single photons (λ=3∼5  μm) can be absorbed in QDs and the photogenerated electrons are drifted to the avalanche region to trigger an avalanche and generate an output pulse. Since the absorption region consists of doped QD layers, it is expected to have higher orders of dark count. However, by separately controlling the bias and keeping the electric field of absorption region low, the dark current of this region can be reduced. Our simulations predict a single-photon detection efficiency (SPQE) of about 0.7 at T=50  K for the proposed detector. At higher temperatures, the dark count rate increases and results in reduced SPQE. To increase the operation temperature, resonant tunneling barriers (RTB) are included in the absorption region to inhibit the thermally excited electrons from contributing to the dark current generation. Our results show that the SPQE for the RTB-based device is about 0.65 at T=77  K, which is approximately equivalent to the SPQE of the device without RTB at T=50  K.

Investigation of a 1.5-µm-wavelength InAs-quantum-dot absorption layer for high-speed photodetector

We investigated a 1.5-µm-wavelength InAs-based quantum-dot (QD) absorption layer for high-speed and high-sensitivity photodetectors in advanced optical-fiber communications. The photodetector, which contained 20 stacked absorption layers of InAs/InGaAlAs QDs using the strain-compensation technique, exhibited a high absorption coefficient, avalanche multiplication effect, and a low dark current. It could operate at a low bias voltage for a p-type–intrinsic–n-type (PIN) diode structure. We expect that the 3-dB bandwidth at a low bias voltage would be approximately 50 GHz, and that the gain and bandwidth product in the avalanche multiplication region would be 150 GHz at a high bias voltage.

Preliminary results for the design, fabrication, and performance of a backside-illuminated avalanche drift detector

The detection of low-level light is a key technology in various experimental scientific studies. As a photon detector, the silicon photomultiplier (SiPM) has gradually become an alternative to the photomultiplier tube (PMT) in many applications in high-energy physics, astroparticle physics, and medical imaging because of its high photon detection efficiency (PDE), good resolution for single-photon detection, insensitivity to magnetic field, low operating voltage, compactness, and low cost. However, primarily because of the geometric fill factor, the PDE of most SiPMs is not very high; in particular, for those SiPMs with a high density of micro cells, the effective area is small, and the bandwidth of the light response is narrow. As a building block of the SiPM, the concept of the backside-illuminated avalanche drift detector (ADD) was first proposed by the Max Planck Institute of Germany eight years ago; the ADD is promising to have high PDE over the full energy range of optical photons, even ultraviolet light and X-ray light, and because the avalanche multiplication region is very small, the ADD is beneficial for the fabrication of large-area SiPMs. However, because of difficulties in design and fabrication, no significant progress had been made, and the concept had not yet been verified. In this paper, preliminary results in the design, fabrication, and performance of a backside-illuminated ADD are reported; the difficulties in and limitations to the backside-illuminated ADD are analyzed.

A Dual-Junction Single-Photon Avalanche Diode in 130-nm CMOS Technology

A dual-junction single-photon avalanche diode structure is reported in a 130-nm low-voltage CMOS technology. The device comprises two stacked avalanche multiplication regions with virtual guard ring constructions. An 8.6- μm-diameter p-well is placed within a 12.3- μm-diameter deep n-well. At 3-V excess bias, the junctions operate with median dark count rates of 10 and 5 kHz and photon detection efficiencies of 32% at 450 nm and 29% at 670 nm, respectively. We demonstrate that the junction at which a photon is detected can be uniquely distinguished by the dead time of the Geiger mode pulse allowing spectral discrimination by simple digital circuitry.

Bit error rates for ultrafast APD based optical receivers: exact and large deviation based asymptotic approaches

Exact analysis as well as asymptotic analysis, based on large-deviation theory (LDT), are developed to compute the bit-error rate (BER) for ultrafast avalanche-photodiode (APD) based optical receivers assuming on-off keying and direct detection. The effects of intersymbol interference (ISI), resulting from the APD's stochastic avalanche buildup time, as well as the APD's dead space are both included in the analysis. ISI becomes a limiting factor as the transmission rate approaches the detector's bandwidth, in which case the bit duration becomes comparable to APD's avalanche buildup time. Further, the effect of dead space becomes significant in high-speed APDs that employ thin avalanche multiplication regions. While the exact BER analysis at the generality considered here has not been reported heretofore, the asymptotic analysis is a major generalization of that developed by Letaief and Sadowsky [IEEE Trans. Inform. Theory, vol. 38, 1992], in which the LDT was used to estimate the BER assuming APDs with an instantaneous response (negligible avalanche buildup time) and no dead space. These results are compared with those obtained using the common Gaussian approximation approach showing the inadequacy of the Guassian approximation when ISI noise has strong presence.

Interferometric temperature mapping during ESD stress and failure analysis of smart power technology ESD protection devices

Breakdown homogeneity and triggering of bipolar transistor action are studied in Smart Power technology ESD protection devices via measurements of temperature distribution and thermal dynamics by a laser interferometric technique. Temperature changes in the devices biased in the avalanche multiplication or snapback region are monitored by ns-time scale measurements of the optical phase shift. The distribution of the temperature-induced phase shift is correlated with the position of ESD damage obtained by backside IR microscopy.

Avalanche-induced excess noise in polycrystalline silicon thin-film transistors

The low-frequency noise behavior of polycrystalline silicon thin-film transistors, operated in the avalanche multiplication region of the output characteristics, is investigated. The avalanche-induced current noise, originating from generation-recombination processes in the depletion region of the drain junction, can be described by the carrier number fluctuation model. Using a model for the excess noise in silicon-on-insulator metal-oxide-semiconductor field-effect transistors operated in the kink regime, an analytical expression for the avalanche-induced current noise is derived taking into account an exponential distribution of the gap states. Comparison of the experimental noise data with the theoretical model indicates that, in addition to the avalanche multiplication, hot-carrier effects contribute significantly to the current increase in the avalanche regime.

MOS small-signal conductances in the weak avalanche multiplication region

Experimental results on MOS small-signal conductances in the weak avalanche multiplication region are presented. The increase in the channel current due to the bulk effect produced by the voltage drop in the substrate has been considered and included in a simple model for the output conductance. Changes in the other small-signal conductances, such as the transconductance overshoot, have also been investigated. >

InGaAs/InAlAs superlattice avalanche photodiode with a separated photoabsorption layer

A novel structure superlattice avalanche photodiode is proposed. A p-InGaAs photoabsorption layer is separated from a nondoped InGaAs/InAlAs superlattice avalanche multiplication region. The electric field strength at the photoabsorption layer is controlled by a thin, highly doped p-InGaAs layer, which is sandwiched between the multiplication and photoabsorption layers. Devices with this structure were fabricated by molecular beam epitaxy. The external quantum efficiency is 73% at the multiplication factor of unity. The multiplication noise is quite small corresponding to an effective ionization rate ratio of 0.1. The maximum 3 dB bandwidth is 9.3 GHz.

Impact ionization induced minority carrier injection by avalanching p-n junctions

Excess minority carriers, generated in the substrate of metal oxide semiconductor transistors operating in saturation, are known to present reliability problems in dynamic memory circuits such as random access memories and charge coupled devices. It has been shown that the minority carriers result from light emission associated with the avalanche multiplication region close to the drain. In this paper we report evidence of a new minority carrier injection process which only occurs in p-n junctions having very low breakdown voltages (≲9 V). The avalanching emitter-base junctions of bipolar transistors were used as the injection sources and injection efficiencies (defined as the ratio of the minority carrier current to the multiplication current) as high as 5×10−3 were recorded. A model of the injection process based on impact ionization within the neutral regions is proposed. A Monte Carlo simulation of avalanche breakdown is used to demonstrate the feasibility of the model.

New InGaAs/InP avalanche photodiode structure for the 1-1.6 µm wavelength region

Low dark current and low multiplication noise properties for an In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</inf> As/InP avalanche photodiode are described. The diode is prepared with an In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</inf> As light absorption layer and an InP avalanche multiplication region. The lowest dark current density of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5.2 \times 10^{-4}</tex> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is obtained at 90 percent of a breakdown voltage. Multiplication noise power is proportional to the 2.7th power of the current multiplication factor. Impact ionization coefficient by holes is larger by 2-3 times than that by electrons in

Theory of a new three-terminal microwave power amplifier

The feasibility of a new three-terminal linear power amplifier has been demonstrated both theoretically and experimentally from 0.5 to 3.0 GHz. The new amplifier is similar to an n-p-n bipolar transistor in configuration but develops extra power gain through avalanche multiplication and by the use of transit time in the collector. Major differences in the construction of the two devices are in their collector doping profiles and depletion layer widths. It is estimated that this new amplifier will be capable of several watts of power output at 10 GHz with useful gain, good linearity, and wide dynamic range. An acronym, CATT, which stands for controlled avalanche transit-time triode, is used to designate this new microwave semiconductor device. In this paper, the theory of the CATT is developed. It is found to be dc and RF stable. The necessary conditions on the ionization coefficients for signal amplification are investigated. The emitter-base dynamics of the CATT are shown to be quite different from a transistor due to hole feedback from the avalanche multiplication region. This phenomena results in a more uniform emitter current injection and better use of the emitter finger area than for transistors.

Noise Characteristics in Silicon Photodiodes

Measurements of noise spectral density in the avalanche multiplication region have been made from 1 MHz to 4 GHz for four silicon photodiodes. The noise spectral density has been compared with the existing theories. At low frequencies the microplasma on-off noise, the theory of which has been successfully applied to one diode containing a single bistable microplasma, is pronounced. At high frequencies (≥100 MHz) one of the photodiodes exhibited a uniform-avalanche shot noise, which has been well described by McIntyre's theory with k=0.1, where k is the ratio of the hole ionization coefficient to the electron ionization coefficient. The rf (1 MHz∼1 GHz) bias has been found to give rise to shifts of the I–V curves to higher voltages and changes in the noise spectral density. In some cases the noise spectral density is reduced. However, whether the noise is reduced or not depends on the property of microplasmas contained in the diode.