A CMOS compatible Ge-on-Si APD operating in proportional and Geiger modes at infrared wavelengths

Sammak, Amir; Aminian, Mahdi; Qi, Lin; Boer, W.B. de; Charbon, Edoardo; Nanver, L.K.

doi:10.1109/iedm.2011.6131515

Cited by 21 publications

(27 citation statements)

References 8 publications

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“…The corresponding high-voltage reverse current was low and characterized by a delayed breakdown around 30 V. This ability to bias past the breakdown point without actually inducing breakdown indicates that this type of diode is suitable for SPAD operation as already demonstrated in Ref. 7. On the bottom part of the wafer, the diodes displayed higher dark current with a spread of up to a decade in saturation current, and the breakdown is characterized by gradual avalanching as would be suitable for avalanche photodiode (APD) operation.…”

Section: Resultsmentioning

confidence: 72%

“…Photodiodes fabricated in this way, but with a thinner Geisland to give a flat surface, have been presented in Ref. 7 that includes optical characterization showing high infrared sensitivity. They have low dark current and when operated as single photon avalanche diodes (SPADs) in Geiger mode, they display low dark-count-rate.…”

Section: Resultsmentioning

confidence: 99%

“…1 for (a) a diode covered with Al deposited directly on the PureGaB 7,8 and (b) a diode where the PureGaB is covered with an infraredtransparent silicon oxide and then contacted through windows etched at the diode perimeter. 9 The starting material is n-type Si (100) wafers.…”

Section: Methodsmentioning

confidence: 99%

“…1a, 675-nm Al/Si(1%) is sputtered directly onto the diodes and then patterned as interconnect to give separate access to the anode of each of the diodes. 7 In the second approach as illustrated in Fig. 1b, first, a 1-lm-thick layer of plasma-enhanced CVD (PECVD) SiO 2 is deposited on top of the devices and then patterned with a ring-shaped opening around each diode.…”

Section: Methodsmentioning

confidence: 99%

“…6 The use of the layer stack of PureB on PureGa, a combination known as PureGaB, as a contacting and barrier layer to Al is particularly attractive because it simultaneously creates an ultrashallow p + n junction the low dark current of which was already demonstrated in our previous papers. [7][8][9] The photodiode anode region was realized by depositing the PureGaB directly on Ge islands grown on silicon wafers with all depositions performed in one and the same chemical-vapor deposition (CVD) reactor system. Both Ga and B are categorized as p-type dopants for group IV semiconductors.…”

Section: Introductionmentioning

confidence: 99%

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Restricted-Access Al-Mediated Material Transport in Al Contacting of PureGaB Ge-on-Si p + n Diodes

Sammak

Nanver

2015

Journal of Elec Materi

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The effectiveness of using nanometer-thin boron (PureB) layers as interdiffusion barrier to aluminum (Al) is studied for a contacting scheme specifically developed for fabricating germanium-on-silicon (Ge-on-Si) p + n photodiodes with an oxide-covered light entrance window. Contacting is achieved at the perimeter of the Ge-island anode directly to an Al interconnect metallization. The Ge is grown in oxide windows to the Si wafer and covered by a B and gallium (Ga) layer stack (PureGaB) composed of about a nanometer of Ga for forming the p + Ge region and 10 nm of B as an interdiffusion barrier to the Al. To form contact windows, the side-wall oxide is etched away, exposing a small tip of the Ge perimeter to Al that from this point travels about 5 lm into the bulk Ge crystal. In this process, Ge and Si materials are displaced, forming Ge-filled V-grooves at the Si surface. The Al coalesces in grains. This process is studied here by high-resolution cross-sectional transmission electron microscopy and energy dispersive x-ray spectroscopy that confirm the purities of the Ge and Al grains. Diodes are fabricated with different geometries and statistical current-voltage characterization reveals a spread that can be related to across-the-wafer variations in the contact processing. The I-V behavior is characterized by low dark current, low contact resistance, and breakdown voltages that are suitable for operation in avalanching modes. The restricted access to the Ge of the Al inducing the Ge and Si material transport does not destroy the very good electrical characteristics typical of PureGaB Ge-on-Si diodes.

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Section: Resultsmentioning

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Restricted-Access Al-Mediated Material Transport in Al Contacting of PureGaB Ge-on-Si p + n Diodes

Sammak

Nanver

2015

Journal of Elec Materi

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SPAD-Based Sensors

Charbon

Fishburn

Walker

et al. 2013

TOF Range-Imaging Cameras

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Optoelectrical Operation Stability of Broadband PureGaB Ge-on-Si Photodiodes with Anomalous Al-Mediated Sidewall Contacting

Krakers

Knežević

Nanver

2021

J. Electron. Mater.

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An anomalous aluminum-mediated material transport process was investigated in sets of Ge-on-Si photodiodes with broadband optoelectrical characteristics measured at wavelengths from 255 nm to 1550 nm. The diodes had “PureGaB” anode regions fabricated by depositing a Ga wetting layer capped with an 11-nm-thick B-layer on 0.5 µm-thick Ge islands grown on Si. The Al metallization was able to reach the Ge-Si interface through ~ 0.1-µm-wide holes inadvertently etched along the perimeter of the Ge-islands, and then traveled along the Ge-Si interface, displacing and recrystallizing Ge and Si. The rest of the Ge surface was protected from the Al contact metallization by the B-layer. For diodes that had received the standard 400°C Al alloying step, the responsivity was near-theoretical at 406 nm and 670 nm, but, at 1310 nm and 1550 nm, the proximity of Ge-Si interfacial defects caused significant attenuation. Extra annealing at 400°C or 500°C enhanced the formation of Si pits that were filled with modified Ge crystals alloyed with Si and p-doped with Al. All these diodes maintained low dark currents, below 50 µA/cm2 at 2 V reverse bias, but the responsivity was degraded, particularly for the long wavelengths. On the other hand, neither responsivity nor degradation of current–voltage (I–V) characteristics was observed for prolonged exposure to normal operating temperatures up to 100°C. Since the direct Al contacting of the Ge sidewalls does not degrade the dark current, for large diodes it could be a low-cost method of obtaining low contact resistance to an anode with p-type sidewall passivation and high fill-factor.

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A CMOS compatible Ge-on-Si APD operating in proportional and Geiger modes at infrared wavelengths

Cited by 21 publications

References 8 publications

Restricted-Access Al-Mediated Material Transport in Al Contacting of PureGaB Ge-on-Si p + n Diodes

Restricted-Access Al-Mediated Material Transport in Al Contacting of PureGaB Ge-on-Si p + n Diodes

SPAD-Based Sensors

Optoelectrical Operation Stability of Broadband PureGaB Ge-on-Si Photodiodes with Anomalous Al-Mediated Sidewall Contacting

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