1. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 1 WOCSDICE 2001 GaAs IBIC analysis of gallium arsenide Schottky diodes C.Manfredotti 1,2, E.Vittone 1,2,F.Fizzotti 1,2, A.LoGiudice 1,2, F.Nava 3 1 Dip. Fisica Sperim., Università di Torino, INFN-Sez. di Torino, via P.Giuria 1, 10125 Torino (I) 2 INFM- Unità di Torino Università, via P.Giuria 1, 10125 Torino (I) 3 Dip. di Fisica, Universitá di Modena, Via Campi 213/A, 41100 Modena, Italy

2. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 2 WOCSDICE 2001 GaAs Summary >IBIC ( ION BEAM INDUCED CHARGE ) PRESENTED AS A POWERFUL METHOD IN ORDER TO INVESTIGATE ELECTRICAL FIELD DEPTH PROFILE AND ELECTRICAL HOMOGENEITY OF DEVICES >FRONTAL IBICC : RESULTS ON ELECTRICAL HOMOGENEITY OF CARBON DOPED n- TYPE SAMPLES >LATERAL IBICC : ANALYSIS OF RESULTS OBTAINED FROM A STANDARD SI SAMPLE IN COMPARISON WITH THEORETICAL MODELS

3. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 3 WOCSDICE 2001 GaAs pre-amplifier Schottky contact ohmic contact (frontal irradiation) 2 MeV proton microbeam 0. 1 m m GaAs (back irradiation) 2 MeV proton microbeam sample holder active region lateral IBIC 2.4 MeV proton microbeam

4. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 4 WOCSDICE 2001 GaAs IBIC Set up frontal lateral Ion beam

5. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 5 WOCSDICE 2001 GaAs FRONTAL IBIC 2 MeV protons ( range in SiC 34 m ) microbeam diameter 2 m scan area up to 2 x 2 mm 2 event-by-event data collection mode historical check of possible effects of radiation damage

6. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 6 WOCSDICE 2001 GaAs GaAs carbon doping effects ( Freiberger ): -lowering of dark current -compensation of EL2 traps ( ? ) -lowering of charge collection efficiency 2 samples L12 C conc. 3 10 14 cm -3 A15 C conc. 8 10 14 cm -3 Frontal IBIC Effect of carbon doping on charge collection efficiency uniformity

7. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 7 WOCSDICE 2001 GaAs FRBBL12 C = 3x10 14 cm -3

8. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 8 WOCSDICE 2001 GaAs FRBAn15 C = 8x10 14 cm -3

9. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 9 WOCSDICE 2001 GaAs

10. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 10 WOCSDICE 2001 GaAs LATERAL IBIC 2 MeV protons polished cross section surfaces no surface effect : penetration depth 34 mm and 2/3 of energy released at the end of the range ( Braggs peak ) the electric field keeps apart the generated carriers : no plasma recombination charge collection efficiency values ( cce ) are obtained by comparison with a Si surface barrier detector cce profiles may be obtained from different regions of the scanned area by averaging over different rows or columns by fitting data by using an equation for cce obtained on the basis of Ramos theorem ) it is possible to check with different possible electrical field profiles

11. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 11 WOCSDICE 2001 GaAs LATERAL IBICC 2.4 MeV protons

12. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 12 WOCSDICE 2001 GaAs 20 30405060708090100 200 20 30 40 50 60 70 80 90 100 200 Slope 0.89 Depletion width ( m ) Bias voltage ( V ) IBICC collection efficiency profiles

13. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 13 WOCSDICE 2001 GaAs e =1.4 ns e =1.3 ns W=65 m e =1.5 ns W=65 m e =1.3 ns W=45 m e =1.8 ns e =1.5 ns W=47 m

14. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 14 WOCSDICE 2001 GaAs CONCLUSIONS Frontal IBIC: Compensation with C : >increases the homogeneity of the response, >worsens energy resolution, but >lowers the charge collection efficiency.

15. C.Manfredotti, Quartu S.Elena, 27-30.5.2001 15 WOCSDICE 2001 GaAs CONCLUSIONS Lateral IBIC >Results are in perfect agreement with the model based on electrical field activated compensation of donors by EL2 centers >The depletion layer width increases almost linearly with bias voltage. >Different kinds of approximation of electrical field profile give very similar results concerning electron and hole lifetimes, but different depletion layer widths. >It may not be appropriate to use Hechts relationship in order to interpret the results, because in the presence of space charge Ramos theorem is no more valid: the extended Ramos theorem or better Gunns principle are needed.