Progress report on the validation of a Two-Photon - PowerPoint Presentation

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Progress report on the validation of a Two-Photon Absorption based Transient-Current-Technique on irradiated silicon

P. Castro1, A. Díez1 , S. Hidalgo6, M. Fernández1, J. González1, R. Jaramillo1, G. Kramberger5, M. Moll2, D. Moya1,R. Montero3, F. R. Palomo4, I. Vila11Instituto de Física de Cantabria (CSIC-UC)2CERN3Universidad del Pais Vasco (UPV-EHU)4Universidad de Sevilla (US)5Jožef Stefan Institute (IJS) (Ljubljana)6Centro Nacional Microelectrónica (CNM)

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Motivation & ScopeAfter the first proof-of-concept measurement to study the TCT currents induced by Two-Photo-Absortion proccess

in an non-irradiated standard silicon PiN diode move to study the TPA-TCT on irradiated devices.New RD50 internal project to estimate the possible radiation induced changes on TPA and SPA process cross-sections.In this talk: progress report, lessons learned and a few results I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat 2

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OutlineBrief recall on the TPA-TCT technique: motivation, simulation and experimental results on irradiated samples.Experimental arrangement to determine the TPA and SPA cross-section against the irradiation fluence (neutrons).Conclusions and outlook

I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat 3

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Motivation for a TPA-based TCT technique

TPA-TCT is a way to generate very localized electron-hole pairs in semiconductor devices (microscale volume).TPA-TCT simplifies the arrangement to inject light into the device and the unfolding of the device internal Electric field and other relevant parameters of the theoretical model.I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat "A picture is worth a thousand words”TPA-TCT could provide a novel experimental tool for studying the currently under development small pixel size detectors.

4

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Experimental arrangement (1)Laserl  1300 nm

P  50-100 pJDT  240 fs Rate  1 kHzDf  11 nmMicrofocusX100 Objective f 100 mm lens 2.5 GHz DSO 5I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

OSC

AMP

SSA

&

FROG

OPA

IF

IA

VNDF

PD

CCD

L

FSW

RL

BS

BS

OBJ

TS

S

DO

DUT

TB

Sourcemeter

Pulsed

femto

laser (at normal incidence) entering the diode junction side (

conventional top-

TCT

configuration

)

FEMTO

LASER

OPTICAL BENCH

READ OUT

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Experimental Arrangement (2)

6I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

DUT CNM N-IN-P DIODELGAD PIN REFERENCE DIODERef - W9F9

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Evidence of TPA-TCTZ-Scan: vertical displacement of the DIODE perpendicularly to the laser beam (z axis)7

I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat Diode Displacement

TPA

-> Charge vs z -> plateau (Observed behavior)

SPA (Standard

TCT

) -> Charge vs z -> no z dependence.

CAVEAT -> The validity of the method relies on SPA signal<<

TPA

Signal

80 x n

index_Si

 280 um

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Generation Volume (knife-scan)8I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

Diode DisplacementLaser waist < than 1 um (accuracy limited by motor displacement resolution)

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TPA-Induced Charge-carriers volume (2)9I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

SimulationSimulation

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TCT Waveform: 97 um focus depth

Electrons and holes TCT current contribution distinct from the TCT current shape.10I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat NOT a fit just a simulation normalizationCNM N-IN-P DIODELGAD PIN REFERENCE DIODERef - W9F9 (500 V bias)

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TPA-TCT: Distinct Electron & Hole dynamicsOut of the box simulation (no fit): 500 V, RC 17pC, Laser waist 0.95 um, Vdep 50 VoltsExcellent agreement between data (left) and TRACS simulation.

11I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat HolesElectronsjunctionOhmic contact

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TPA-TCT feasiblity RD50 project: goalsThe goal of the this project is to quantify the relative contribution to the TCT current of the radiation-induced Single-Photon-Absorption and Two-Step-Single-Photon-Absorption processes with respect to the

TPA processIn addition, study the feasibility of using a femtosecond laser tuned in the C-band (1530-1570 nm) a more suitable band due the higher availability of off-the-shelf photonics components12I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

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TPA-TCT feasiblity RD50 project: Method“Z-scan” measurement on the diodes under test. During the Z-scan, in addition to the measurement of the transient photocurrent, the transmitted light will be measured (Ge photodiode). From this measurement we will extract the

b Two-Photon-Absorption and a SPA parameter13I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

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Samples and upgraded experimental arrangement 12 identical (almost) PiN diodes from LGAD runs.Three fluences (neutrons): 1E13, 1E14 and 1E15Ge

diode to measure the transmitted light during the z-scan.Thermal chuck to reach -20 Celsius degrees.Light tight enclosure: dry box and Faraday cage.14I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

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Experimental arrangement (2)15I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

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Experimental arrangement (2)16

I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat Performed several “Z-scan” measurement on a diode at three different temperatures.First conclusion: not enough sensitivity to measure a change in the transmitted lightneed to increase the excitation volume keeping the same irradiation (to increase signal x 1E3)

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Z-Scan with expanded beam waist (14um)Improve the sensitivity to the measurement of transmission attenuation in the z-scan.Increasing the energy about 1E2 and the volume a factor 1E3 (keeping a similar intensity)Extract relative and absolute b value

17I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat Diode Displacement

Ge Photodiode Transmission

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Measuring the Absortion (photo-charge vs z position)Redundantly we measure the induce photo charge as an estimate of the absorption (reducing the pulse power 1/4)18

I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat Diode DisplacementGe Photodiode Transmission

Photo Charge

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ConclusionTPA-TCT method proved on non-irradiated samples.Successful second measurement run for measuring the two photon absorption probability (b parameter)Diodes to be sent to irradiate this week.Expect to complete the test of irradiated samples by the the end of the year.

19I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

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ReferencesMore details on the basics of the TPA process can be found in this talk by F.R. Palomo (link)More details on the code TRACS (TRansient Current Simulator) used to compute the theoretical current waveforms in P. de Castro talk (

link)Details on the first proof-of-concept measurements (link) 20I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

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BACK-UP21I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

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TPA-TCT Proof-of-concept ChallengesConfirm the generation of TPA induced current in a silicon diode with the appropriate laser power.Determine the dimensions of the charge-carrier’s generation volume.

Compare the experimental TCT current waveforms against the theoretical simulated current waveforms (assess its potential as experimental tool to discriminate between different theoretical models).I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat 22

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Evidence of TPA-TCT (2)Pure quadratic dependence between the Signal Charge and the laser power. 23

I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

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Which is the adequate laser power ?24I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

Similar pulse shapes for laser pulses up to a power of 60-80 pJ, for higher power values TCT waveform gets wider and wider (likely due to plasma effects).

Seconds

35 pJ47pJ59 pJ

82 pJ147 pJ223

pJ

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TPA-Induced charge-carriers volume25I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

The laser’s volume of excitation ( e-h pair creation) is fully determined by the laser parameters (l and W0) and the TPA cross-section in Silicon (b)In our case, l and b are known, a fit of the raising edge of the charge z-scan profile determines W0beam waist from the fitw

0 = 0.95±0.05 um

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TPA-Induced Charge-carriers volume (2)26I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

SimulationSimulation

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TCT Waveforms: 20um focus depth27I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

NOT a fit just a simulation normalizationSingle Photon Absorption red laser TOP-TCT (hole injection) CNM N-IN-P DIODELGAD PIN REFERENCE DIODERef - W9F9 (500 V bias)

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TCT Waveform: 97 um focus depth

Electrons and holes TCT current contribution distinct from the TCT current shape.28I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat NOT a fit just a simulation normalizationCNM N-IN-P DIODELGAD PIN REFERENCE DIODERef - W9F9 (500 V bias)

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TCT Waveform: focus depth 160umAround the minimal pulse width, similar arrival times for electrons and holes29

I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat CNM N-IN-P DIODELGAD PIN REFERENCE DIODERef - W9F9 (500 V bias)

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TCT Waveform: focus depth 237umTCT wavefrom gets wider again, trailing edge dominated by electrons now.30

I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat CNM N-IN-P DIODELGAD PIN REFERENCE DIODERef - W9F9 (500 V bias)

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TCT Waveform: focus depth 278umSPA - red laser bottom-TCT like signal (electron injection)31

I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat CNM N-IN-P DIODELGAD PIN REFERENCE DIODERef - W9F9 (500 V bias)

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32I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat

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Conclusions and OutlookWe have completed the successful proof-of-concept of a novel Transient-Current-Technique based on the Two-Photon-Absortion (TPA) processExcellent agreement between the experimental data and the simulation points to its potential as tool for disentangling different theoretical models. Opens up the possibility of a new range of opportunities for boosting the scope of

TCT techniques: More accurate 3D mapping of Efield.Simpler unfolding methods.More accurate study of pixelated sensors.Less relevance of metal-induced beam reflections.But, still a lot of work and challenges ahead to make it a reliable, accessible and practical diagnostic tool.33I. Vila, Reunion Seguimiento FPA2013 ILC, 27 Octubre 2015, Ciemat