M. De Napoli, F. Giacoppo, G. Raciti, E. Rapisarda, C. Sfienti. Laboratori Nazionali del Sud (LNS) INFN University of Catania. IPRD Oct.

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1 M. De Napoli, F. Giacoppo, G. Raciti, E. Rapisarda, C. Sfienti Laboratori Nazionali del Sud (LNS) INFN University of Catania IPRD Oct. Siena

2 Silicon carbide (SiC) is expected to be applied to high-power devices. WIDE BANDGAP ->LOW LEAKAGE CURRENT HIGH SENSIVITY 100 times Radiation Hard than Si

3 Applications 12 Thyristors MOSFET VR=400V di/dt=400 A/µs trr=8 ns MESFET K 300 K 300 K Reverse voltage (V) Schottky diodes lightning arresterss in electric power systems Current (A) Electronic devices: Time (ns) JFET Astronomy and Aereospace: mirror material for astronomical telescopes X-Rays detectors in harsh environments Nuclear Physiscs Detectors Neutrons, protons, alphas, light ions detectors blue LEDs

4 Detection of alpha, 12C, 16O ions at different energies: Linearity Depleted region vs applied reverse bias Charge collection Energy resolution Signal rise-time Radiation Damage

5 SiC from ETC-Catania The Schottky diodes were fabricated by epitaxy onto high-purity 4H-SiC n-type substrate from the ETC - Catania Deposition temperature 1600 C Deposition rate 7 µm/hr Uniformity on wafer ±1.5%

6 Detector chips were glued on a brass foil and bonded on a board 0.5x0.5 mm2 2x2 mm2 1x1 mm2 Each chip contains 5 individual detectors of different area

7 LNS Tandem accelerator 13 MV 1 measurement st 2nd measurement C Inc. Energies: MeV 16 O : MeV 12 C Inc. Energies: MeV 16 O : 35.2 MeV 12

8 A 300 µm Si has been used for comparison The Silicon detector has been calibrated by using a one peak Am alpha source and calibrated pulser 4 Al foils have been used to provide alphas at different incident energies

9 Alpha energies 2.19 MeV (18 µm Al) 2.72 MeV (16 µm Al) 3.18 MeV (13 µm Al) 3.76 MeV (10 µm Al) Tandem beams allow to extend the energy range explored with alpha particles: 12 C at 5.04 MeV and MeV 16 O at 7.3 MeV, 9.78 MeV, MeV, MeV, MeV High degree of linearity F. Nava et al., NIM A437 (1999)354 F.H. Ruddy et al., NIM A505 (2003)159 W. Cunningham et al., NIM A 509 (2003)127

10 Black peaks refers to SiC signals calibrated according to Si calibration Sipeak/SiCpeak = 2.08

11 Ee-h (Si) = 3.76 ev Sipeak/SiCpeak = Ee-h (SiC) = ev

12 Incident alpha energy: 3.18 MeV According to SRIM calculation the range in SiC is 13µm Signals increase with increasing bias voltage At saturation the active area is the range of 3.18 MeV alphas in SiC (13µm)

13 Black dots: depletion measured with alpha particles Red dots: depletion measured with Tandem beams Vbuilt-in 1.3 um resulting from the Schottky contact potential F. Nava et al., NIM A437 (1999)354 d= 2ε (Vrev + Vbuilt in ) qn eff 400 Volts -> active region of 13 µm!

14 where: V Applied reverse Bias N Doping Concentration ε the static permittivity of the material ε =9.66 ε0 [24] where ε0 is the electric constant ε0 = F/m. e are the electron charge V built-in is the magnitude of the Schottky barrier 1.5 V o lts, [25]. 2nd Measurements Energy lost in the 0.2 µm Ni2-Si front layer Type Nominal doping (N/cm3 ) Thickness(µm) C Energy (MeV) 12 A B C Energy Corrected

15 SiC- type b 12 C 27.7 MeV Vbias A- Low Doping B- Medium Doping C- High Doping

16 2nd Measurements A- Low Doping B- Medium Doping 1st Measurements C- High Doping

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18 Charge Collection Measured Depleted region

19 Charge Collection Same Lp value for the three 12C energies

20 Charge Collection Lp = 4±1µm τp = 52 ±20 ns Lp = 7±1µm τp = 160 ±40 ns Lp=((KT/e)µp τp) where: Lp < 0.5 µm 1/2 τp ho le lifetim e T temperature µp o hm ic hole m obility µp= 120 cm 2 V-1 s -1 e elec tro n c ha rg e Diffusion process negligible: probably higher density of defects

21 ENERGY RESOLUTION = 2.8% C peak = 9.26 MeV (larger than typical Si resolution) FWHM = 381 kev F.H. Ruddy et al., NIM A505 (2003) kev

22 Low Doping Concentration Medium Doping Concentration High Doping Concentration

23 C beam at MeV 12 Tektronix TDS 5104B Digital Oscilloscope

24 Drift Velocity α Vbias α 1/sqrt(Vbias) Depleted region thickness α sqrt(vbias) RISE TIME (nsec) Decrease of rise time: 44 nsec Bias (Volts)

25 Irradiated with 53 MeV 16O beam The amplitude drops to 50% Reverse current increases by a factor of ions/cm2 The noise increases by a factor of 2 S. Sciortino et al., NIM A552 (2005)138 Factor 10 harder than Si T. Quinn et al., Nuclear Science Symposium. Conference record, Vol.2, Portland,OR,USA,19-25 Oct. 2003

26 Low Doping Concentration High Doping Concentration

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28 SiC from ETC-CATANIA Good Linearity Response: SiCpeak= 0.5 Sipeak Energy Resolution: 2.8% (Si <1%) Rise time: 44 nsec Radiation Damage: ions/cm2 50% ; 1015 ions/cm2 Inversion Factor 10 harder than Si Very high values of Bias needed!! but it depends on the N+ concentration

29 Beginning ions/cm ions/cm ions/cm2 INVERSION Same signals for 53 MeV and 12 MeV O beams (Space Charge Sign Inversion ) Sciortino et al. NIM A 552(2005)138 G. Lindström et al., NIM A466 (2001) 308 L. Bosisio et al., IEEE Trans. Nucl. Sci., 50 (1) (2003) 219

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31 Silicon Carbide

32 Entries in Histogram MIMOSA II before and after irradiation with 200kRad X-Rays 800 Before After Irradiation Charge Collected in 4 Pixels [ADC] (c) Michael Deveaux Conclusion on Mimosa 2 after ~ 400kRad: Leakage currents increases by a factor ~5. Noise increases by some percent. Readout electronics OK. Charge collection drops by ~50% (kills the chip)

33 Where does the extracharge come from?

34 Ti Ni2Si SiO2 Ni n x1016 cm-3 n+ ~1018cm-3 Ni2Si Ohmic contact

35 Measured Qc E1 D E2 Q0 + Etot Calculated

36 Dynamical recovery Current (A) Reverse voltage (V) 400 K 300 K 300 K VR=400V di/dt=400 A/µs Time (ns) trr=8 ns

37 electrical application Astronomy Silicon carbide's hardness and rigidity make it a desirable mirror material for astronomical work lightning arresterss in electric power systems

38 17.68 MeV 12C beam spectra at increasing bias voltage

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