Influence of δ p-doping on the behaviour of GaAs/AlGaAs SAM-APDs for synchrotron radiation

Steinhartova, T.; Antonelli, M.; Cautero, G.; Menk, R.H.; Pilotto, A.; Driussi, F.; Palestri, Pierpaolo; Selmi, L.; Koshmak, Konstantin; Nannarone, Stefano; Arfelli, Fulvia; Zilio, Simone Dal; Biasiol, G.

doi:10.1088/1748-0221/12/11/c11017

Cited by 7 publications

(19 citation statements)

References 6 publications

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“…Photo-generated electrons are multiplied by the impact ionization events taking place inside the staircase multiplication region. made of 12 repetitions of a stack with a 35nm GaAs layer, a 25nm Al 0.45 Ga 0.55 As film and 20 nm of a linearly graded alloy with an Al content that is increased from 1% to 45% [1]. The resulting staircase multiplication region features a periodically modulated conduction band profile [see Fig.…”

Section: Device Structurementioning

confidence: 99%

“…Next generation X-rays detectors require higher count rate and higher quantum efficiency for medium and high photon energy. Avalanche photo-diodes (APDs) in III-V compounds are very promising with respect to silicon ones thanks to the higher atomic number of the material that allows for thinner detectors and to the larger band-gap that limits the leakage current [1], [2]. However, the APD development and optimization requires an in-depth understanding of the physical mechanisms involved in the device operation [3].…”

Section: Introductionmentioning

confidence: 99%

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Experimental and simulation analysis of carrier lifetimes in GaAs/AlGaAs Avalanche Photo-Diodes

Driussi

Pilotto

Belli

et al. 2020

2020 IEEE 33rd International Conference on Microelectronic Test Structures (ICMTS)

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Extensive experimental characterization and TCAD simulation analysis have been used to study the dark current in Avalanche Photo-Diodes (APDs). The comparison between the temperature dependence of measurements and simulations points out that SRH generation/recombination is responsible for the observed dark current. After the extraction of the carrier lifetimes in the GaAs layers, they have been used to predict the APD collection efficiency of the photo-generated currents under realistic operation conditions and as a function of the photogeneration position inside the absorption layer.

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Section: Device Structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental and simulation analysis of carrier lifetimes in GaAs/AlGaAs Avalanche Photo-Diodes

Driussi

Pilotto

Belli

et al. 2020

2020 IEEE 33rd International Conference on Microelectronic Test Structures (ICMTS)

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“…The devices under investigation were grown epitaxially onto GaAs wafers by using molecular beam epitaxy (MBE) techniques. The photolitographic fabrication procedure applied to obtain the separated absorption and multiplication (SAM) APD is the one reported in [6]. A sketch of such device is shown schematically in Fig.…”

Section: Detector Growth and Fabricationmentioning

confidence: 99%

“…For these measurements the device was kept in a stainless steel and UHV compatible chamber, which in turn was placed into a dark box, whereas the APD was illuminated by a tabletop laser (λ = 532 nm). The green laser was selected such that the photo-induced charge generation was limited to the absorption region only [6], so as to have ideal conditions of charge injection close to the entrance window in the absorption region during noise characterisation. For all measurements reported here, the laser spot was always focused on the centre of the device opening.…”

Section: Set-upmentioning

confidence: 99%

Investigation of the behaviour of GaAs/AlGaAs SAM-APDs for synchrotron radiation

Steinhartova¹,

Antonelli²,

Cautero³

et al. 2019

AIP Conference Proceedings

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This work reports on the fabrication and characterization of a novel high-speed, low-noise X-ray Avalanche Photodiode based on III-V compound semiconductors operating over an extended photon energy range. These materials were suggested as their higher atomic numbers allow for the absorption of higher photon energies; hence, shorter response times can be achieved by growing APDs with thinner active regions. In addition, the use of staircase hetero-junctions enhances electron multiplication and results in lower noise if compared with conventional p-i-n diodes. In this work, molecular beam epitaxy was used to produce GaAs/AlGaAs APDs with separated absorption and multiplication regions. The multiplication region, separated from the absorption region by a δ p-doped layer of carbon, contains a staircase structure composed of nanometric layers of AlGaAs and GaAs, which alternate periodically. The periodic modulation of the band gap enables a well-defined charge multiplication and results in low multiplication noise. Several devices were characterized in terms of dark current, photocurrents generated utilizing visible and hard X-ray sources as well as noise generated under laser light.

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“…The APDs made of GaAs/AlGaAs epitaxial layers were grown by MBE on a 500-μm-thick heavily Si-doped n-type GaAs substrate. The resulting layered structure is summarized in [6]. The minimum dose to achieve complete depletion of the multiplication region (2.5 × 10 12 cm −2 [6]) was used to fabricated the devices presented here.…”

Section: Apd Designmentioning

confidence: 99%

Effects of p doping on GaAs/AlGaAs SAM-APDs for X-rays detection

et al. 2020

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Avalanche photodiodes based on GaAs/AlGaAs with separated absorption and multiplication regions (SAM-APDs) will be discussed in terms of capacitance, response to light (gain and noise) and time response. The structures have been fabricated by molecular beam epitaxy introducing a p layer doped with carbon to separate the multiplication and the absorption regions. The thickness of the latter layer defines the detection efficiency and the time resolution of the structure, which in turn allows tailoring the device for specific scientific applications. Within the multiplication region a periodic modulation of the bandgap is obtained by growing alternating nanometric layers of AlGaAs and GaAs with increasing Al content; this staircase structure enables the tuning of the bandgap and subsequently provides a well-defined charge multiplication. The use of such staircase hetero-junctions enhances electron multiplication and conversely reduces-at least in principle-the impact of the noise associated to hole multiplication, which should result in a decreased overall noise, when compared to p-in diodes composed by a single material. The first part of this paper focuses on the electrical characteristics of the grown structure and on the comparison with the simulated behaviour of such devices. In addition, gain and noise measurements, which have been carried out on these devices by utilizing photons from visible light to hard X-rays, will be discussed and will be compared to the results of a nonlocal history-dependent model specifically developed for staircase APDs.

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Influence of δ p-doping on the behaviour of GaAs/AlGaAs SAM-APDs for synchrotron radiation

Cited by 7 publications

References 6 publications

Experimental and simulation analysis of carrier lifetimes in GaAs/AlGaAs Avalanche Photo-Diodes

Experimental and simulation analysis of carrier lifetimes in GaAs/AlGaAs Avalanche Photo-Diodes

Investigation of the behaviour of GaAs/AlGaAs SAM-APDs for synchrotron radiation

Effects of p doping on GaAs/AlGaAs SAM-APDs for X-rays detection

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