Ryan Weed
Centre for Antimatter-Matter Studies
VACANCY CLUSTERS IN SELF-ION IMPLANTED GERMANIUM STUDIED
WITH PALS
MOTIVATION
Germanium is a good candidate to replace Silicon in CMOS devices
3-4 times higher mobility (determines device speed)
MOTIVATION
Implantation induced defects eff ect electrical activation
Dopant-defect relationship not well understood in Ge
Diff usion mechanisms dissimilar to Si
Positrons well suited to study evolution of vacancy type defects under thermal treatment
ION IMPLANTATION
800 keV Ge+ implantation
Fluence between 3x1012 and 3x1014 cm -2
Vacancy and interstitials damage distribution simulated in SRIM
RBS RESULTS
As-implanted Annealed
High fluence sample ‘amorphized’ by ion implantation
No damage detected in low fluence sampleSPEG of amorphous region complete at 400 C anneal
PALS RESULTS
Vacancy clusters formed in both samples
Cluster size expected in magic numbers (N=6,10,14)
Clusters dissolve at 500 C in both samples
VARIABLE ENERGY PALS
2,10,18keV positron energies performed on 400 C annealed samples
Similar lifetime distribution for amorphous and sub-amorphous implants
Intensity distributions diff er
Mobility diff erences or SPEG eff ect
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