A pn-SiC diode as a radiation messi/SIC/sic_21-01-04/kinoshita_ieee.pdf¢  Picture of...

A pn-SiC diode as a radiation messi/SIC/sic_21-01-04/kinoshita_ieee.pdf¢  Picture of pn-SiC A pn-SiC
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Transcript of A pn-SiC diode as a radiation messi/SIC/sic_21-01-04/kinoshita_ieee.pdf¢  Picture of...

  • 0 2 4 6 8 100

    0.01

    0.02

    0.03

    0.04

    0.05

    -d I/ dx

    [× I0]

    Depth [μm]

    I = I0exp(-αx)

    W

      

       −−×

    L

    Wx exp

    Picture of pn-SiC

    A pn-SiC diode as a radiation detector Akimasa Kinoshitaa, Motohiro Iwamia, Itsuo Nakanoa, Reisaburo Tanakaa,

    Tomihiro Kamiyab, Akihiko Ohib, Takeshi Ohshimab, Yasutaka Fukushimac a Faculty of Science, Okayama University, 3-1-1, Tsushimanaka, Okayama 700-8530, Japan b Japan Atomic Energy Research Institute, 1233 Watanuki Takasaki, Gunma 370-1292, Japan c KEK, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan

    Abstract We evaluated pn-SiC (silicon carbide) particle detectors exposed to 5.486 MeV alpha particles from a sealed radioactive source of 241Am and 3.26 eV (380 nm) pulsed Ultra-Violet (UV) light at 100Hz from a Light Emitting Diode (LED). The pn junction SiC diode was made by the implantation of phosphorus (P) ions (140, 60, 90 keV) into p-type 6H-SiC epitaxial layers (5µm) grown onto p+-type substrates. The mean pulse height from detector increased with the supplied reverse bias voltage for each irradiation, alpha particles and UV light. We discuss relation of the pulse height distribution obtained by the UV light and the alpha particles to the depletion width with diffusion length of carriers.

    2nF

    1 0 0 M

    Ω

    2nF

    2nF

    1 .5

    M Ω

    1 .5

    M Ω

    1 .5

    M Ω

    1pF

    500M Ω

    93 Ω

    Preamplifier (EG&G 142AH)

    Shaper Amplifier (EG&G ORTEC 672)

    Discriminator

    Gate Generator

    Analog to Digital Converter (HOSHIN C008)

    CAMAC Crate Controller

    Bias Source (KIKUSUI PMC350)

    2nF

    Veto

    Gate

    α source 241 Am

    Bipolar Output

    U ni

    po la

    r O

    ut pu

    t

    Output Register

    SiC (Silicon Carbide)

    0 10 20 30 40 500

    1000

    2000

    Co un ts

    Channel

    0V -10V -50 -100 -200

    0 50 100 150 2000

    0.2

    0.4

    0.6

    0.8

    1 (1) (2) = + (3) (4)

    CC E

    Reverse Bias [V]

    L = 2.5 μm

    1/C2 versus applied voltage for pn junction diode. These capacitances, closed circles, ware subtracted stray capacitance, solid curve, from total capacitance, broken curve, at several reverse bias voltages.

    ○ I-V characteristics (KEITHLEY 2400 high voltage source meter) ○ 1/C2-V characteristics (HEWLETT PACKARD 4277A 1MHz LCZ meter)

    0 1000 2000 30000

    20

    40

    60

    80

    1000 1 2

    Channel

    Co un ts

    Energy [MeV]

    0 V -10 V

    -50 V -100 V -200 V

    The pn-SiC diode - 4.1 MeV alpha particles from a radioactive source of 241Am - 3.26 eV pulsed UV light from LED. For alpha measurement The charge collection efficiency was good agreement with the theoretical method using diffusion length. The diffusion with 2.5 µm was obtained. For UV measurement The effect of carrier diffusion on charge collection is not significant. No or small diffusion length is obtained. The difference of charge collection between alpha and UV irradiations can be interpreted in terms of the distribution of e-h pairs in the neutral region.

    The pulse processing system consisting of a pre-amplifier, a main (shaping) amplifier, an Analog-to-Digital Converter, and a personal computer through the GPIB interface.

    Pulse height spectra obtained by irradiating alpha particles to the pn-SiC diode at different reverse bias voltages, V=0, -10, -50, -100 and -200.

    The Charge Collection Efficiency (CCE) as a function of the applied reverse bias in the range of 0 ~ -200V, these CCE is the ratio of the loss energy, 4.1MeV, of incident alpha particles to the energy calculated by using e-h pair producing energy 8.4 eV for SiC.

      

       −−+

    =

    d

    W

    W

    dx L

    Wx

    dx

    dE

    E

    dx dx

    dE

    E CCE

    )( exp

    1

    1

    p

    0 p

    UV light was introduced into the electrode of the pn-SiC diode using a guide pipe with diameter 100 µm which is used for forcing UV light to around center of pn junction area

    The pulse height spectra obtained with the pn-SiC diode at different reverse bias voltages, V=0, -10, -50, -100 and -200V by UV light of 1µs width pulses at 100Hz.

    Theoretical curve (1) with solid-line, curve (2) with broken-line and curve (3) with dash-dotted ware obtained by equation 1. The curve (1) without diffusion and the curve (2) with L=1.0 µm have good agreement to experimental open circles for measurement of 1µs pulse width.

    Al Box

    In air at room temperature.

    LED UV 100μmφ

    The pulse processing system consisting of a pre-amplifier, a main (shaping) amplifier, an Analog-to-Digital Converter, and a personal computer through the GPIB interface. UV light was generated by LED connected to a function generator.

    ・UV-LED - NICHIA-NSHU590AE - 380 nm (peak) - 3.26 eV @ In air @ At room temperature

    100 Ω

    5 0

    Ω

    2nF

    1 0 0 M

    Ω

    2nF

    2nF

    1 .5

    M Ω

    1 .5

    M Ω

    1 .5

    M Ω

    1pF

    500M Ω

    93 Ω

    Preamplifier (EG&G 142AH)

    Function Generator (WAVETEK datron 39A)

    Spectroscopy Amplifier (EG&G ORTEC 672)

    Analog to Digital Converter (HOSHIN C008)

    CAMAC Crate Controller

    Bias Source (KIKUSUI PMC350)

    LED ( λ = 380nm )

    2nF

    Gate ADC

    Discriminator

    Gate Generator

    Al Box

    In vacuum (~1kPa) at room temperature.

    α 300μmφ ・ Sealed alpha source

    - 4.1 MeV @ In vacuum (~1kPa) @ At room temperature

    Alpha particles were introduced into the electrode of the pn-SiC diode using a guide pipe with diameter of 300µm witch is used for forcing alpha particles to the pn junction area.

    Bragg ionization curve - SRIM2000 simulation - SiC - 4.1MeV - alpha particles

    Equation 1

    Equation 2

    0 5 100

    10

    20

    30

    40

    50

    60

    Depth [μm]

    dE /d x [k ev /μ m ]

    ・He- ion ・4.1 MeV ・SiC

    W

      

       −−×

    L

    Wx exp

    The function of intensity absorbed per unit lengh in SiC for UV with intensity I0.

    ( )

    ( )∫  

       −−⋅−

    +−−= d

    W dx

    L

    Wx xI

    WIPairs

    expexp

    )exp(1

    0

    0

    αα

    α

    [] large bandgap [] high electrical breakdown field [] high electron saturation drift velocity [] high thermal conductivity

    A superior material for [] high temperature [] high frequency [] high power electronics.

    Schematic cross-section of pn-SiC Electrical Characteristics

    UV Measurement

    alpha Measurement

    Summary

    Figure A-1 Figure A-2 Figure A-3 Figure A-4

    Figure B-1 Figure B-2 Figure B-3

    Figure C-1 Figure C-2 Figure C-3

    Normalizing

    The instruments for I-V and C-V measurement were controlled by the PC through the GPIB interface. The pn-SiC diode was in a shielded fixture to minimize external spurious noise during I-V and C-V measurement. The linearity of 1/C2-V curve in Figure A-3 shows the good uniformity of doping concentration within the active layer. The built-in voltages estimated from Figure A-2 and Figure A-4 have good agreement, Vbi=2.2~2.4 V.

    The I-V characteristic for forward bias in the region of 1.0 ~ 3.0 V.

    The I-V characteristics for reverse bias in the region of 0 ~ -200 V. Leakage curents were of the order of several nA.

    0 100 200

    0.2

    0.4

    0.6

    0.8

    1

    Reverse Bias [V]

    N or m al iz ed p ul se h ei gh t a nd

    in te ns ity a bs or be d in d ep le tio n la ye r

    no diffusion (1) 1.0μm (2) 2.5μm (3)

    Pulse width : 1μs Experimental

    Theoretical

    The numerical least-squares fit

    Depletion Region Neutral Region

    UV light

    alpha partcle

    Diffusion

    e-h pairs High

    Low

    Conclusion SiC is a promising material as particle detector. UV illumination is an alternative evaluation method for the capability of SiC particle detectors. For UV illumination, the channel number of charge collection increase with increasing reverse bias voltage applied to SiC diodes. This behavior is very similar to the result obtained in alpha irradiation.

    Al

    φ: 300μm bond pad

    Al

    SiO2 Al SiC n+-type

    SiC p-type

    SiC p+-type

    Al

    150 nm ~5μm

    ~300μm