Systematic Investigation of Equal Double Junctions in Proton-Irradiated Si Detectors

1. Systematic TCT Investigation of Equal-Double-Junctions in 24 GeV Proton Irradiated MCZ n and p-type Si Detectors Z. Li1, G. Carini1, W. Chen1, V. Eremin2, J. Harkonen3, P. Luukka3, E. Tuominen3,E.Tuovinen3, E. Verbitskaya2 1Brookhaven National Laboratory, Upton, NY 11973, USA 2Ioffe Physico-Technical Institute, St. Petersburg, Russia 2Helsinki Institute of Physics, Helsinki, Finland 12th RD50 - Workshop on Radiation hard semiconductor devices for very high luminosity colliders Ljubljana, Slovenia, 2-4 June 2008 *This research was supported by the U.S. Department of Energy: Contract No. DE-AC02 -98CH10886

2. Outline 1. Introduction 2. Experimental conditions 3. Results and discussions 4. Summary

3. Introduction • Up to now, no standard SCSI has been observed in 24 GeV p-irradiated MCZ n-type Si detectors • Double junction/peak was seen with TCT, only in electron current pulse shapes though [1,2]. • Unlike any other cases, the second peak/junction was not the dominate one • Is there a SCSI in 24 GeV p-irradiated MCZ n-type Si detectors • Whatever it is, it is not in the conventional term • Any new effect in this special case (MCZ, 24 GeV proton)? • Systematic TCT studies needed to have the complete picture: • Both electron and hole current shapes should be looked (with and without trapping corrections) • Both n and p type MCZ Si detectors should be investigated • Need to compare with the control case (FZ, 24 GeV proton) • E. Verbitskaya, V. Eremin, Z. Li, J. Harkonen, M. Bruzzi. Concept of Double Peak electric field distribution in the development of radiation hard silicon detectors // Nucl. Instrum. Methods Phys. Res. A 583 (2007) 77-86. • 2. Donato Creanza, 3rd Workshop on Advanced Silicon Radiation Detectors (3D and P-type Technologies) • 14-16 April 2008, Barcelona, Spain

4. Current [A] Time [s] Electron injection – front side illumination p+/n-/n+ Trapping

5. Current [A] Time [s] Hole injection – back side illumination p+/n-/n+ Trapping

6. Experimental Conditions • Samples: • 3 sets of samples studied MCZ n-type (p+/n/n+), MCZ p-type (n+/p/p+), and FZ n-type (p+/n/n+ ) control samples • MCZ samples were made by HIP, FZ samples were made by CNM • Radiations: • 24 GeV Proton from CERN, fluence 1.6x1014p/cm2 to 2.4x1015 p/cm2 • 22-23 day RT anneal • Experimental technique: IV, CV, and TCT [3] with red (635 nm) laser (all measured at BNL at RT) on both p+ and n+ contacts • 3. V. Eremin, N. Strokan, E. Verbitskaya and Z. Li, NIM A 372 (1996) 388-298

7. FZ-n, #F-82, 1.6x1014 p/cm2 Double junction/peak clearly seen 1st peak changes little with bias (e’s) 2nd peak takes over at higher biases than the full depletion voltage (e’s) -SC dominates at high biases (SCSI) Experimental Results and DiscussionsFZ n-type Si (control samples) h’s p+ n+ e’s p+ n+ Double peaks clearly seen SCSI at high V 212V 242V 193V 212V 173V 173V 153V 94V (Vfd(CV)=145V) 133V 45V b) Hole transient For h’s, the 2nd peak (minor, near p+) can hardly be seen It is consistent with a minor 1st peak (also near p+) for e’s p+ n+ 123V 114V 104V 94V 45V a) Electron transient

8. FZ-n, #F-84, 3.2x1014 p/cm2 Double junction/peak clearly seen 1st peak changes little with bias (e’s) 2nd peak takes over at higher biases than the full depletion voltage (e’s) -SC dominates at high biases (SCSI) Experimental Results and DiscussionsFZ n-type Si (control samples) p+ n+ Double peaks clearly seen SCSI at high V n+ p+ 381V 362V 478V 342V 381V 322V 282V 185V 303V (Vfd~303V) 90V b) Hole transient p+ n+ 283V 254V 234V 185V 90V a) Electron transient

9. FZ-n, #F-87, 9.7x1014 p/cm2 Double junction/peak clearly seen 1st peak changes little with bias (e’s) 2nd peak takes over at higher biases than the full depletion voltage (e’s) -SC dominates at high biases (SCSI) Experimental Results and DiscussionsFZ n-type Si (control samples) Double peaks clearly seen SCSI at high V n+ p+ p+ n+ 738V 649V 647V 460V 598V (Vfd~550V) 548V 270V 502V 86V n+ p+ b) Hole transient 457V 363V 270V 177V 85V a) Electron transient

10. FZ-n, #F-88, 1.3x1015 p/cm2 Double junction/peak clearly seen 1st peak changes little with bias (e’s) 2nd peak takes over at higher biases than the full depletion voltage (e’s) -SC dominates at high biases (SCSI) Experimental Results and DiscussionsFZ n-type Si (control samples) Double peaks clearly seen SCSI at high V n+ p+ p+ n+ 876V 797V 892V 724V 714V 541V 671V (Vfd~671V) 356V 83V p+ n+ b) Hole transient 624V 577V 541V 356V 85V a) Electron transient

11. FZ-n, #F-89, 2.4x1015 p/cm2 Double junction/peak clearly seen Nearly identical (symmetrical) TCT curves for both e and h Not fully depleted +SC dominates near p+ contact, -SC dominates near n+ contact Experimental Results and DiscussionsFZ n-type Si (control samples) p+ n+ p+ n+ (Vfd>1000V) 400V 326V 250V 168V 86V a) Electron transient b) Hole transient Identical/symmetrical Not fully depleted

12. Experimental Results and DiscussionsMCZ n-type Si MCZ-n, #01-N-32, 1.6x1014 p/cm2 NO SCSI, slightly double junction/peak seen p+ n+ p+ n+ 492V 443V 393V 343V 294V 394V 294V 194V (Vfd(CV)=132V) n+ p+ 96V 274V a) Electron transient 254V 234V Double peaks just start 214V 194V b) Hole transient

13. Experimental Results and DiscussionsMCZ n-type Si MCZ-n, #01-N-31, 3.2x1014 p/cm2 double junction/peak clearly seen Similar TCT curves for both e and h +SC dominates at high biases p+ n+ p+ n+ Nearly identical 380V 485V 387V 435V 386V 337V p+ n+ 337V 288V 287V 238V 189V p+ n+ 86V 267V 170V 248V 254V 228V 298V 208V 342V p+ n+ 189V (Vfd(CV)=170V) p+ n+ 170V p+ n+ 150V 170V 130V c) Hole transient Measured with sample upside-down (to get more laser illumination) 150V 111V 130V 91V 111V 91V a) Electron transient b) Hole transient

14. Experimental Results and DiscussionsMCZ n-type Si MCZ-n, #01-N-62, 9.7x1014 p/cm2 double junction/peak clearly seen Nearly identical TCT curves for both e and h Equal-Double-Junction +SC dominates near p+ contact, -SC dominates near n+ contact p+ n+ 745V p+ n+ 650V 553V (Vfd(CV)=380V) Identical 455V 365V 408V 318V 271V 178V 87V a) Electron transient 363V 316V 269V 176V 85V b) Hole transient

15. Experimental Results and DiscussionsMCZ n-type Si MCZ-n, #01-N-62, 9.7x1014 p/cm2 double junction/peak clearly seen Nearly identical TCT curves for both e and h Equal-Double-Junction +SC dominates near p+ contact, -SC dominates near n+ contact Hole transient Measured with sample upside-down (use the Laser-front fiber in the system to get more laser illumination, maybe some blockage in the Laser-back fiber, and the Al mesh on the back still blocks some laser light, also more leakage current) VB VLaser Effect of bias Effect of laser power 74V 156V -6V 241V -7V 329V 412V -8V -9V -10V Identical to the e’s VLaser = -10V VB = 329V p+ p+ n+ n+ a) Hole transient, various biases b) Hole transient, various laser biases

16. MCZ-n, #01-N-20, 1.3x1015 p/cm2 double junction/peak clearly seen Nearly identical TCT curves for both e and h Equal-Double-Junction +SC dominates near p+ contact, -SC dominates near n+ contact Experimental Results and DiscussionsMCZ n-type Si identical p+ n+ p+ n+ 900V 993V 908V 720V 725V 629V 629V 532V 532V (Vfd~530V) 74V 152V 231V p+ n+ 305V p+ n+ 380V 440V 442V 353V 352V p+ n+ 263V 263V 173V 172V 84V 83V c) Hole transient Upside-down b) Hole transient a) Electron transient

17. MCZ-n, #01-N-27, 2.4x1015 p/cm2 double junction clearly seen Nearly identical (symmetrical) TCT curves for both e and h (this is similar to the conventional cases: FZ with any particle irradiation (p, n pion), MCZ with low energy p, and n) Equal-Double-Junction Not fully depleted +SC dominates near p+ contact, -SC dominates near n+ contact Experimental Results and DiscussionsMCZ n-type Si Identical/symmetrical Not fully depleted p+ n+ p+ n+ (Vfd>1000V) 660V 650V 632V 635V 500V 500V 334V 335V 79V 77V b) Hole transient a) Electron transient

18. Experimental Results and DiscussionsMCZ p-type Si MCZ-p, #p-069-62, 1.6x1014 p/cm2 Double junction/peak clearly seen -SC dominates at high biases 165V 165V 195V 195V 245V 245V 292V 340V 293V 340V p+ n+ p+ n+ Double peaks 46V (Vfd(CV)=45V) 62V 46V n+ 86V 86V 105V 106V 125V 125V 145V p+ p+ n+ b) Hole transient a) Electron transient

19. Experimental Results and DiscussionsMCZ p-type Si MCZ-p, #p-069-64, 3.2x1014 p/cm2 Double junction/peak clearly seen Nearly identical TCT curves for both e and h Equal-Double-Junction -SC slightly dominates at high biases 282V 376V 472V 565V 44V 660V 91V (Vfd(CV)=115V) n+ p+ 140V Nearly identical 188V 236V 44V p+ n+ 91V 140V 188V a) Electron transient 236V n+ p+ b) Hole transient

20. MCZ-p, #p-069-72, 9.7x1014 p/cm2 Double junction/peak clearly seen Nearly identical TCT curves for both e and h Equal-Double-Junction +SC dominates near p+ contact, -SC dominates near n+ contact Experimental Results and DiscussionsMCZ p-type Si 86V 85V 178V 178V 273V 196V (Vfd~273V) 320V 215V 345V 234V p+ n+ n+ p+ Identical 254V 273V (Vfd~273V) 292V 361V 321V 363V 401V p+ n+ n+ p+ a) Electron transient b) Hole transient

21. MCZ-p, #p-069-74, 1.3x1015 p/cm2 Double junction/peak clearly seen Nearly identical TCT curves for both e and h Equal-Double-Junction +SC dominates near p+ contact, -SC dominates near n+ contact Experimental Results and DiscussionsMCZ p-type Si 81V 172V 263V 355V 393V (Vfd~393V) p+ n+ n+ p+ Identical a) Electron transient b) Hole transient

22. MCZ-p, #p-069-75, 2.4x1015 p/cm2 double junction clearly seen Nearly identical (symmetrical) TCT curves for both e and h (this is similar to the conventional cases: FZ with any particle irradiation (p, n pion), MCZ with low energy p, and n) Equal-Double-Junction Not fully depleted +SC dominates near p+ contact, -SC dominates near n+ contact Experimental Results and DiscussionsMCZ p-type Si 76V 163V 251V 337V 413V (Vfd>800V) p+ n+ Identical/symmetrical Not fully depleted n+ p+ b) Hole transient a) Electron transient

23. Experimental Results and DiscussionsAfter trapping corrections FZ-n, DP/DJ dominated by the one near the n+ MCZ-p, equal-double-peak /DJ near p+ and n+ MCZ-n, equal-double-peak /DJ near p+ and n+ (Laser front) (Laser front) p+ n+ e’s p+ p+ n+ n+ -SC +SC -SC +SC -SC +SC (Laser back) (Laser back) p+ h’s n+ -SC p+ n+ p+ n+ +SC -SC +SC -SC +SC

24. Experimental Results and Discussions SCSI Summary

25. Summary • Standard SCSI has not been observed in the 24 GeV proton-irradiated MCZ n-type Si detectors in the fluence range studied here --- it seems that it skips the standard SCSI and goes directly into the double peak/double junction stage • This double peak/double junction effect is observed in both MCZ n-type and p-type Si detectorsirradiated by 24 GeV protons • However, this double peak/double junction effect is not the same as in the case for the control sample set (FZ n-type Si, 24 GeV proton-irradiated): the two peaks/junction are almost the same (after trapping corrections), indicating half +SC and half –SC in the detector, especially at higher fluences than 3x1014 p/cm2, regardless of bias voltages • In fact this effect is unique only for this special combination (24 GeV proton-irradiated MCZ n-type and p-type Si detectors) • Equal-double-junction helps to low the Vfd significantly • Physical models are needed to explain this: maybe combined effect of clusters, point-defects, and high oxygen concentration (not related to initial doping)? And about equal trapping probabilities for e’s near the n+ contact and h’s near the p+ contact? • Fitting of the data for double junction profiles will be done soon

26. Backup slides Full-Depletion Voltage (Vfd) Summary The Equal-double-junction helps to low the Vfd!

27. Summary on full-depletion voltage (Vfd), normalized to d=300 µm The Equal-double-junction helps to low the Vfd!