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Capacitance at Different Temperature: Simulation and Measurements

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Capacitance at Different Temperature: Simulation and Measurements 6nd ROSE Workshop CERN 23.10.2000 A. Santocchia, B. MacEvoy, G. Hall Imperial College London – PowerPoint PPT presentation

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Title: Capacitance at Different Temperature: Simulation and Measurements


1
Capacitance at Different Temperature Simulation
and Measurements
  • 6nd ROSE Workshop CERN 23.10.2000
  • A. Santocchia, B. MacEvoy, G. Hall
  • Imperial College London
  • F. Moscatelli, D. Passeri
  • Perugia University

2
Outline
  • Defect Kinetics Model
  • Point Defects - Cluster Defects
  • Setup Measurements
  • Data VS Kinetics Model Comparison
  • Simulation Model
  • Status Future Work

3
Standard SRH
  • Defect Reactions
  • Interstitial - Vacancy
  • Impurity Concentrations
  • Phosphorus
  • Oxygen
  • Carbon

4
Gamma and Neutron Results
  • Good agreement between model and data for gamma
    irradiation
  • V2O responsible for changes in Neff
  • BUT
  • Problems with Hadron Interaction
  • a and Neff are too small

5
Now what? ? Clusters
  • Gamma irradiation
  • Point Defects
  • Hadron irradiation
  • Point Defects Cluster Defects
  • CLUSTER When a Primary Knock-on Atom loses the
    last 5 KeV of recoil energy ? many defects in a
    small spatial region
  • Some CLUSTER Numbers
  • Typical Dimension 5-10 nm
  • Silicon Atoms in a Cluster 104
  • Defects in a Cluster 10
  • Typical Density 1019 cm-3
  • Average Defect Separation 1 nm
  • Introduction Rate 0.4 cm-1

6
Charge Exchange (Not SRH!)
Is direct charge exchange between defects
forbidden? NO What if we include this new
phenomenon in the Model?
7
Charge Exchange 2
Increase in carrier generation rate and
acceptor-like contribution to Neff predicted for
expected density of defects in Clusters
8
Proton and Neutron Results
  • Neutron Irradiation
  • All materials equally rad-hard
  • Proton Irradiation
  • Oxygen-enriched More rad-hard
  • Carbon-enriched Less rad-hard

Why ? V2O more important for p
9
Room VS Cryogenic Temperature
  • The model performs well _at_ RT
  • Is model still good _at_ T 100K - 300K ?
  • Is there any chance to find other evidence of
    Charge Direct Exchange ?
  • Already experimentally seen but with complex
    spectroscopy techniques (ODMR, ESE-EPR)
  • Cryogenic System Built to check the Model

10
Experimental Setup
  • HP LCR Meter 4284A with variable frequency (20 Hz
    - 1MHz)
  • Small Heating Rate Cryogenic System (0.5K/min)
  • CV scan of Irradiated Diode
  • T (100 - 300)K Vbias (0-150) V
  • f 200Hz, 1KHz, 10KHz

11
Diode Characteristics
  • Standard Hammamatsu Process
  • 310 mm thick - 5?5 mm2 guarded
  • Resistivity 5.8 KWcm Vdep54V
  • Fluence 8.7?1013 n/cm2
  • Beneficial annealing completed and then kept _at_
    T-20C

12
Model and Data _at_ RT
SRH CC, CO, P, VP, VO, V2O, V3O non SRH V2,
E70, E170
  • First check that Model and Data are in agreement
    for the chosen diode
  • Complete Diode characterization performed _at_ RT
  • Lets start the game!

13
Neff VS T (Model Data)
  • Watts Da Via observe Type Inversion _at_ T190K
    for fluence 1014 n/cm2
  • The model shows inversion _at_ T225K but the
    fluence is lower No Big discrepancy!

14
Comments
  • Can Neff be extracted from data?
  • Look at CV plots at different Temperature and try
    to guess where is Vdep
  • And what about the Frequency al low T?

15
Temperature 100K 200K
16
Temperature 250K 300K
17
Simulation
  • Finite Element Simulator Silvaco
  • Simple Diode Structure (50mm width 300mm Thick)
  • 3 Defects with standard SRH Statistic and the
    following parameters

Energy Defect sn (cm-2) sp (cm-2) H (cm-1)
Ec-0.42 V2 -/0 10-16 2x10-15 1
Ec-0.55 V20 10-16 10-15 0.1
Ev0.36 CO 10-15 10-16 1
18
Current Consideration
  • The current depend on the level occupancy AND on
    the defects density
  • In the simulation the V2 level (Ec-0.42) is the
    major responsable for the current
  • The Increasing of the V2 Introduction Rate hide a
    very clear and simple explanation

The simulation doesnt take into account any
direct inter-level charge exchange
19
Occupancy (Level Ec-0.42)
20
Occupancy (Level Ec-0.55)
21
Occupancy (Level Ev0.36)
22
Occupancy (All Defects)
23
Capacitance (DataSimulation)
24
Conclusion
  • Measurements and Simulation show that SRH is not
    enough (no news here!)
  • Work in progress
  • Experimental Setup ready at IC for Signal
    measurements _at_ T (100 - 300)K indipendent value
    for Vdep soon available as a cross-check
  • CV curve Interpretation difficult but could give
    interesting information compared with Signal
    measurements and Device Simulation
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