Francesco Moscatelli, Andrea Scorzoni

1. First characterizations of a minimum ionizing particle detector based on p+n junction SiC diode Francesco Moscatelli, Andrea Scorzoni DIEI and INFN, University of Perugia, via G. Duranti 93, 06125 Perugia, Italy in collaborazione con CNR- IMM Sezione di Bologna, via Gobetti 101, 40129 Bologna, Italy Dipartimento di Fisica, Polo Scientifico di Sesto Fiorentino,Via Sansone 1 Firenze Italy Institut für Kristallzüchtung, D-12489 Berlin, Germany. This work was supported by the INFN SiCPOS project

2. Outline • Introduction • Technological process and mask design • I/V - C/V measurements and annealing effects • CC setup and measurements • Irradiation with 1 MeV neutrons • Conclusions and future developments

3. A bit of history • 2003: IV, CV, DLTS and CCE on IMM samples. • November 2003: first process. Breakdown of the wafer during the last annealing. • June 2004: First process repeated. The process has been brought to completion. Unfortunately the surface of the wafer was everywhere p-type instead of n-type. Reason: low doping epi process at IKZ. • Fine 2004: Second process (with new mask set).

4. Plan of activity - 2005 • Good quality of process verified with IV, CV and CC measurements on unirradiated devices in early 2005 • Irradiation with neutrons May 8 2005 • Measurements on irradiated devices in June and July (in progress)

5. n- n+ SiC Process: p+/n Front:Al (350 nm) / Ti (80 nm) deposition Back: Ni Epi (55 m) doping: 21014 cm-3 Ion implantation Al+ @ 300°C p+doping (0.4 m) = 41019cm-3 p-doping (0.6 m) = 51017cm-3 Annealing 1600°C 30 min Annealing 1000°C in vacuum 2 min Annealing 430°C in nitrogen 30 min

6. Mask design 31 diodes in each die

7. 4 5 6 7 8 9 Wafer E F G H I J K L M N • 4 quarters. Rows from E to N • Columns from 4 to 9 • Columns 4, 8 (no J8 and k8) and 9 show p-type layer under the Schottky contacts

8. Ti-Al p- p+ n n+ Ni I-V measurements on p+/ndiodes • Before annealing at 430°C, 70 % of diodes have good I-V curves (considered colums 5, 6, 7 and dies J8 and K8) • Theoretical limit for this device  6 kV

9. Reverse current: effect of annealing at room temperature and at 430°C Defects anihilate at room T. The process is accelerated at 430°C

10. CV measurements • The depletion voltage is near 220-250 V • Epi doping not uniform (average value 21014 cm-3)

11. CC measurements and irradiation • Reference with CC measurements without irradiation • 7 dies for irradiation with neutrons

12. Amptek 90Sr 0.1mCi Acquisition system S+PM trigger CCE measurement setup The noise of the charge collection setup is linearly proportional to the capacitance of the detector and is given by ENC=200e+4.6e/pF

13. CC measurements • Signal distribution (Landau) well separated from noise (Gaussian) • At about 250 V the Landau distribution does not change  full depletion

14. CC vs V • Around 200-250 V the signal saturates, in good agreement with CV results.

15. Irradiation with neutrons • Irradiation with 7 different fluences in the range 1014-1016 1 MeV neutrons/cm2 carried out May 8 in Ljubiana • Fluences: 11014 n/cm2, 31014 n/cm2, 71014 n/cm2 , 1.51015 n/cm2, 31015 n/cm2, 71015 n/cm2, 11016 n/cm2 • We are keeping the diodes at –5°C in order to make possible the analysis of annealing effects at RT

16. Before irradiation After irradiation First IV results on irradiated devices • At a fluence of 31014 n/cm2 the junction disappeared. The n-type material becomes intrinsic • The reverse and forward current are comparable

17. Conclusions • p+/n junctions have been realized and electrically characterized. Good forward and reverse characteristics have been obtained • CC experimental results on unirradiated SiC pn junctions: 3000 e- at 200 V • Irradiation with 7 different fluences in the range 1014-10161 MeV neutrons/cm2 • Preliminary results on irradiated samples Future developments • Measurements on irradiated samples