Radiation damage and annealing in 1310nm InGaAsP/InP lasers for the CMS Tracker

1. Radiation damage and annealing in 1310nm InGaAsP/InP lasers for the CMS Tracker K. Gill, G. Cervelli, R. Grabit, F. Jensen, and F. Vasey. CERN, Geneva

2. Background • CMS Tracker readout and control project • Complex system with >50000 optical links • Harsh radiation environment • Extensive use of commercial off-the-shelf components (COTS) • Part-of series of on-going validation tests required before components integrated into final system • Previous tests reported at SPIE and RADECS 97- 99

3. CMS Tracker optical link technology lasers single-mode fibre + array connectors photodiodes • Transmitter - 1310nm InGaAsP edge-emitter • Fibres and connectors - single-mode Ge-doped fibre • Receivers - InGaAs p-i-n photodiode • Electronics - rad-hardened 0.25mm in radiation zones • COTS issues: • radiation damage: up to 1014particles/cm2 + 100 kGy • reliability: 10 year lifetime in radiation environment

4. CMS Experiment

5. CMS Tracker radiation environment • charged hadrons (p, p, K) (courtesy M. Huhtinen, CERN)

6. CMS Tracker readout and control links Analogue Readout 50000 links @ 40MS/s FED Detector Hybrid Tx Hybrid 96 Rx Hybrid processing MUX A buffering APV 4 DAQ 2:1 D amplifiers 12 12 C pipelines 128:1 MUX PLL Delay Timing DCU TTCRx TTC Digital Control 2000 links @40MHz FEC Control 64 4 TTCRx CCU CCU 8 processing buffering CCU CCU Back-End Front-End

7. System specifications • Last 2 columns filled in for each device type after testing • Analogue readout links

8. Objectives • Compare damage from different particles • 0.8MeV n and 6MeV n, 330MeV p, 24GeV p, 60Co g • Measure annealing characteristics • Temperature and current dependence • Make prediction for damage expected in CMS tracker • 10 years at -10°C, including LHC luminosity profile

9. Experiment • Devices • Italtel/NEC 1310nm edge-emitting InGaAsP/InP MQW lasers • mounted on Si-submounts • compact mini-DIL packages, single-mode fiber pigtails • no other components in the package, e.g. lenses • Pre-irradiation characteristics at 20°C : • Laser threshold currents 8-13mA • Output efficiencies (out of the fibre) 30-70mW/mA • This type of device previously studied • 6MeV n, 330MeV p, 24GeV p, 60Co g

10. DCPBH-MQW lasers • double-channel-planar-buried-heterostructure laser

11. Test Procedures • Test A: Irradiate 0.8MeV n - compare damage with other particles • 4 lasers, irrad room T, biased 5-10mA above threshold, 1015n/cm2 in 6.5 hrs. • Anneal at room T, biased 5-10mA above threshold for 115 hrs • Test B: Irradiate 0.8MeV n - anneal at different T • 12 lasers, cooled -13°C, unbiased, 1015n/cm2 in 6.3 hrs. • Anneal in groups of 3 at 20, 40, 60, 80°C for 300 hrs. • Test C: Irradiate 0.8MeV n - anneal at different bias currents • 8 lasers, irrad room T, unbiased, 1015n/cm2 in 6.5 hrs. • Anneal in groups of 2 at 0, 40, 60, 80mA bias for 115 hrs.

12. Test setup for in-situ measurementof radiation damage and annealing

13. Test A - 0.8MeV irradiation at room T • Damage approximately linear with fluence

14. Test A - Comparison with other particles Data averaged over devices then normalized to 96 hour irradiation with 5x1014particles/cm2. • Relative damage factors for 0.8MeV n with respect to ~6MeVn (1/3.1), 330MeV p (1/11.4), 24GeV p (1/8.4).

15. Test B - cooled irradiation Irradiation fluence 1015 (0.8MeV n)/cm2 • Test made at -10°C, then devices stored at -35°C

16. Test B - Annealing versus temperature Devices split into 4 groups of 3 and annealing at different temperatures. Threshold damage assumed to be proportional to number of defects • Annealing generally linear with log (time)

17. Test C - Annealing versus current Irradiation to 1015n/cm2 at room T, unbiased, then anneal in 4 groups of 2 at different bias currents Enhancement caused by: (i) ‘recombination enhanced annealing’ (?) - supposed to be unlikely in InGaAsP/InP (ii) thermal acceleration due to power dissipation. At 80mA DTjunction ~ 8C. • Up to factor 10 enhancement in terms of annealing time

18. Annealing model Assume 1st order (exponential) annealing obeying Arrhenius law: remaining fraction of defects: where • For defects with a uniform distribution of activation energies r = N/(tmax-tmin), the annealing islinear with log (time)

19. Activation energy spectrum Data points for each group of 3 devices averaged. Fit annealing model to Test B data. • Activation energy spectrum for best fit is 0.66<Ea<1.76eV

20. Damage prediction in 1yr in CMS tracker Use model to predict annealing of defects at -10°C over 1 LHC year LHC/CMS running LHC shutdown damage + annealing annealing • 32% of total defects introduced during 1 year are annealed

21. Damage prediction 10yrs in CMS tracker Extend to 10 years, taking into account LHC luminosity profile Based on damage of 0.8MeV n at -10C (Test B) and relative damage factors (Test A), possible to estimate damage to laser threshold in CMS Tracker: in worst case, at low radii (and no bias-enhancement included), DIthr = 14mA

22. Conclusions • ‘Calibrated’ damage from 0.8MeV neutrons • relative to 6MeV n, 330MeV p, 24GeV p • Determined annealing dependence • temperature and forward bias current • Constructed a model to describe the annealing v T • uniform distribution of activation energy 0.66<Ea<1.76eV • Based on data, applied model to CMS Tracker to predict laser threshold damage • In the worst case, at low radii: DIthr = 14mA • Further work: • extension of the study to include lasers from other manufacturers.