Excess noise measurement in In0.53Ga0.47As

The excess noise due to impact ionization has been measured explicitly for the first time in In/sub 0.53/Ga/sub 0.47/As. By using a phase sensitive detection technique, the noise due to avalanche current was determined even in the presence of high tunneling currents. The excess noise due to pure electron injection measured on a series of thick In/sub 0.53/Ga/sub 0.47/As p/sup +/-i-n/sup +/ diodes suggests large electron to hole ionization coefficient ratio between 3.7 at electric field of 310 kV/spl middot/cm/sup -1/ to 5.3 at 260 kV/spl middot/cm/sup -1/. Excess noise was also measured at fields as low as 155 kV/spl middot/cm/sup -1/ suggesting that significant impact ionization occurs at these low fields. The multiplication and excess noise calculated using published ionization coefficients and ignoring dead space effects, gave good agreement with the experimental data for mixed and pure electron injection

Effect of impact ionization in the InGaAs absorber on excess noise of avalanche photodiodes

The effects of impact ionization in the InGaAs absorption layer on the multiplication, excess noise and breakdown voltage are modeled for avalanche photodiodes (APDs), both with InP and with InAlAs multiplication regions. The calculations allow for dead space effects and for the low field electron ionization observed in InGaAs. The results confirm that impact ionization in the InGaAs absorption layer increases the excess noise in InP APDs and that the effect imposes tight constraints on the doping of the charge control layer if avalanche noise is to be minimized. However, the excess noise of InAlAs APDs is predicted to be reduced by impact ionization in the InGaAs layer. Furthermore the breakdown voltage of InAlAs APDs is less sensitive to ionization in the InGaAs layer and these results increase tolerance to doping variations in the field control layer

Field dependence of impact ionization coefficients in In0.53Ga0.47As

Electron and hole ionization coefficients in In/sub 0.53/Ga/sub 0.47/As are deduced from mixed carrier avalanche photomultiplication measurements on a series of p-i-n diode layers, eliminating other effects that can lead to an increase in photocurrent with reverse bias. Low field ionization is observed for electrons but not for holes, resulting in a larger ratio of ionization coefficients, even at moderately high electric fields than previously reported. The measured ionization coefficients are marginally lower than those of GaAs for fields above 250 kVcm/sup -1/, supporting reports of slightly higher avalanche breakdown voltages in In/sub 0.53/Ga/sub 0.47/As than in GaAs p-i-n diodes

Optimization of InP APDs for high-speed lightwave systems

Calculations based on a rigorous analytical model are carried out to optimize the width of the indium phosphide avalanche region in high-speed direct-detection avalanche photodiode-based optical receivers. The model includes the effects of intersymbol interference (ISI), tunneling current, avalanche noise, and its correlation with the stochastic avalanche duration, as well as dead space. A minimum receiver sensitivity of -28 dBm is predicted at an optimal width of 0.18 mu m and an optimal gain of approximately 13, for a 10 Gb/s communication system, assuming a Johnson noise level of 629 noise electrons per bit. The interplay among the factors controlling the optimum sensitivity is confirmed. Results show that for a given transmission speed, as the device width decreases below an optimum value, increased tunneling current outweighs avalanche noise reduction due to dead space, resulting in an increase in receiver sensitivity. As the device width increases above its optimum value, the receiver sensitivity increases as device bandwidth decreases, causing ISI to dominate avalanche noise and tunneling current shot noise

Absorption coefficients in AlGaInP lattice-matched to GaAs

The absorption coefficient of AlGaInP lattice-matched to GaAs, across the composition range from AlInP to GaInP has been obtained from photocurrent versus wavelength measurements on seven homo-junction AlGaInP PIN diode structures. Due to the sensitivity of the photocurrent measurement technique, values of absorption down to 100 cm−1 have been determined close to the band-gap. From these, the bandgaps in this material system were extracted across the composition range and these corroborate data in the literature that shows the band-gap becoming indirect when the aluminium content, x>0.48

Simple Monte Carlo Simulator for modelling Linear Mode and Geiger Mode Avalanche Photodiodes in C++

Linear mode and Geiger mode Avalanche Photodiodes are widely used to detect weak optical signals, with the latter able to detect a single photon at a time. Practical simulators for these devices should accurately produce relevant device characteristics and not be overly computationally intensive. The Simple Monte Carlo Simulator, written in C++, offers such a combination and can simulate avalanche photodiodes made with Silicon, Gallium Arsenide and Indium Gallium Phosphide, with the potential to include other semiconductor materials. The software is available on The University of Sheffield Research Data Catalogue and Repository at https://doi.org/10.15131/shef.data.5683939 and on GitHub at https://github.com/jdpetticrew/Simple-Monte-Carlo-Simulator

Characterization of room temperature AlGaAs soft X-ray mesa photodiodes

Results characterising a set of nine prototype Al0.8Ga0.2As p+–i–n+ mesa photodiodes (400 µm diameter, 1.7 µm i layer) are presented. The results show the performance of the devices as room temperature spectroscopic photon counting soft X-ray detectors. The responses of the photodiodes to illumination with an 55Fe radioisotope X-ray source were measured using a low noise charge sensitive preamplifier; the energy resolutions measured with the devices were consistent with each other and had a mean FWHM at 5.9 keV of 1.27 keV. The devices are the thickest (highest detection efficiency) AlGaAs X-ray spectroscopic mesa photodiodes reported in the literature to date. They also have better energy resolution than all previously reported non-avalanche AlGaAs X-ray detectors of the same area

An InGaAs/AlAsSb Avalanche Photodiode With a Small Temperature Coefficient of Breakdown

Dark current and avalanche gain M on AlAs0.56Sb0.44 (hereafter referred to as AlAsSb) separate absorption multiplication (SAM) avalanche photodiodes (APDs) were measured at temperatures ranging from 77 K to 300 K. To avoid possible ambiguity in breakdown voltage due to edge breakdown and tunneling current, a phase-sensitive detection method with a tightly focused light spot in the center of the device was employed to measure M accurately. An extrapolation of 1/M to zero was used to deduce the breakdown voltage, from which the temperature coefficient of breakdown voltage Cbd was derived. The value of Cbd 1/4 8 mV/K, obtained for AlAsSb SAM APDs, is much smaller than that for commercial Si and InGaAs/InP APDs, as well as other SAM APDs in the literature, demonstrating the potential of AlAsSb avalanche regions in improving the thermal stability of APDs

Sensitivity calculations of high-speed optical receivers based on electron-APDs

Sensitivity of high-speed optical receivers is heavily influenced by the performance of the optical detectors used in the receivers, the data rate, and the target bit-error-rate (BER). A simulation model for sensitivity of optical receivers based on electron-avalanche photodiodes (e-APDs) is presented. It allows for the optimization of avalanche width and operating voltage to achieve the optimum receiver sensitivity for given bit rate and target BER. The effects modelled include inter-symbol interference (ISI), various dark current components (tunnelling, diffusion, and generation), current impulse duration, avalanche gain, and amplifier's noise. The model was demonstrated through simulations of Indium Arsenide (InAs) e-APDs. For 10 -12 target BER, the receiver's sensitivities were found to be -30.6, -22.7, -19.2, and -16.6 dBm, for 10, 25, 40, and 50 Gb/s data rate, respectively. Desirable avalanche properties of InAs e-APDs are counteracted by detrimental effects of high dark currents. Hence InAs e-APDs with lower dark currents are required to be more competitive with other optical detector technologies for high-speed optical receivers. The data reported in this article is available from the ORDA digital repository (DOI: 10.15131/shef.data.9959468)

A theoretical comparison of the breakdown behavior of In0.52Al0.48As and InP near-infrared single-photon avalanche photodiodes

We study the breakdown characteristics and timing statistics of InP and In0.52Al0.48As single-photon avalanche photodiodes (SPADs) with avalanche widths ranging from 0.2 to 1.0 mu m at room temperature using a random ionization path-length model. Our results show that, for a given avalanche width, the breakdown probability of In0.52Al0.48As SPADs increases faster with overbias than InP SPADs. When we compared their timing statistics, we observed that, for a given breakdown probability, InP requires a shorter time to reach breakdown and exhibits a smaller timing jitter than In0.52Al0.48As. However, due to the lower dark count probability and faster rise in breakdown probability with overbias, In0.52Al0.48As SPADs with avalanche widths <= 0.5 mu m are more suitable for single-photon detection at telecommunication wavelengths than InP SPADs. Moreover, we predict that, in InP SPADs with avalanche widths <= 0.3 mu m and In0.52Al0.48As SPADs with avalanche widths <= 0.2 mu m, the dark count probability is higher than the photon count probability for all applied biases