Vacancy clusters in self-ion implanted Germanium studied with PALS

Ryan Weed

Centre for Antimatter-Matter Studies

VACANCY CLUSTERS IN SELF-ION IMPLANTED GERMANIUM STUDIED

WITH PALS

BEAMLINE OVERVIEW

BEAMLINE OVERVIEW

Transport coils Trap SourceSample station

detector

PALS ANALYSIS

PALS ANALYSIS

MOTIVATION

Germanium is a good candidate to replace Silicon in CMOS devices

3-4 times higher mobility (determines device speed)

MOTIVATION

Implantation induced defects effect electrical activation

Dopant-defect relationship not well understood in Ge

Diffusion 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

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 differ

Mobility differences or SPEG effect

THANKS

CAMS – James Sullivan, Steve Buckman, Michael Went, Jason Roberts

EME – Simon Ruffell Technical Staff - Steve Battison, Ross

Tranter, Colin Dedman, Graeme Cornish

PPC10 organizers for help in financing my attendance