V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

Recovery of Charge Collection with Continuous Hole Injection in Irradiated Detectors

V. Cindro, I. Mandic, G. Kramberger, M. Mikuž,I. Pižorn, M. Zavrtanik

After irradiation (and inversion) high resistivity silicon becomes effectively p-type, space charge in depleted region is negative.

Radiation induced levels can act as traps (for example signal degradation).

Trapped charge changes the electric field (has been shownby different groups – mostly at T < - 150 oC

Hole injection + trapping on donor – changes the sign of the space charge.

Effect is temperature dependent

TCT Setup

HV

diodecurrent amplifier (0.01-1GHz,55dB)

TDS 754 C

•about 3 105 electron-hole pairs/pulse

~ 15 m.i.p., adjustable with filter

Optical cryostat (77-310K),

digital oscilloscope

500MHz, 2Gs/s

light pulse (670,1060 nm)rate (20-80 Hz )

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia 1st RD-50 Workshop , CERN 2-4 October 2002

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

Samples: diodes processed by ST MicroelectronicsW339 ROSE wafer resistivity ~ 15 k? cm (VFD

~ 10 – 15 V)

Irradiated at TRIGA reactor in Ljubljana to ? eq

= up to 1015 n cm-2

irradiation flux 1.9 1012 n cm-2 s-1

damage factor 0.92 ± 0.05 samples annealed to the minimum inthe VFD at room temperature (1week)

Field manipulation by DC hole injectionΦeq= 7.5 1013 n cm-2, ? I variedHole signal, p = ? I/(eo S v) ~ ? I t d /(eo S d)

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

?I = 0, T = 253 K, ? eq = 5 1014 n cm-2,

?I = 12 µA, T = 253 K

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

Field manipulation: changing ? I, T, V

Trapping reduces the signal:

Hole trapping in the presence of enhanced hole concentration: ? eq = 5 1014 n cm-2 T = 273 KTrapping times measured with charge correction method.

5.0 ± 1700

4.5 ± 0.7620

3.5 ± 0.5450

4.0 ± 0.5310

5.5 ± 1150

3.3 ± 0.50

t c [ ns ]? I/S [µA/cm2]

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

Electron trapping in the presence of enhanced hole concentration: ? eq = 5 1014 n cm-2 T = 273 K

4.5 ± 0.7620

4.8 ± 0.5450

5.0 ± 0.5310

7.0 ± 1150

5 ± 0.50

t e [ ns ]? I/S [µA/cm2]

? trapping of electrons and holes is not changed considerably in the presence of the enhanced free hole concentration

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

Measurements with IR laser (experimental simulation of MIP)? = 1060 nmSample irradiated to ? eq = 5 1014 n cm-2 , VFD ~ 700V

T = 293K

T = 253K

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

Sample irradiated to ? eq = 1015 n cm-2 , VFD ~ 1400 V

T =283K

T =273K

T = 253K

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

Measurements with Sr90 beta source

?I/S ~ 100 µA cm-2

leakage I/S ~ 10 – 20 µA cm-2

T = 253 K

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

CCE ~ 0.7 at 250 V preliminary result

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

Conclusions:

CCE recovery with DC hole injection is possible also on non cryogenic temperatures.

Noise increase due to the additional current depends on application.Additional power is temperature dependent…

V. Cindro, Jožef Stefan Institute, Ljubljana, Slovenia

1st RD-50 Workshop , CERN 2-4 October 2002

If you do not see any signals…

Turn on the light!!!