Grown-in vacancy-type defects in poly- and single crystalline silicon investigated by positron annihilation

¹ Department of Physics, University of Winnipeg, 515 Portage Avenue, Winnipeg, Manitoba, Canada R3B 2E9
² Topsil Semiconductor Materials, Linderupvej 4, PO Box 100, 3600 Frederikssund, Denmark

Corresponding author: sdannefaer@shaw.ca

Received: 7 February 2006
Revised: 16 September 2006
Accepted: 20 November 2006
Published online: 24 January 2007

Abstract

Positron annihilation was used to characterize vacancy-type defects in two types of polycrystalline Si grown at temperatures above ~800 °C by chemical vapour deposition. The majority of vacancies (80%) consisted of monovacancies, and their thermal stability indicated them to be trapped at grain boundaries or at dislocations. Annealing above 500 °C caused a significant reduction in the monovacancy concentration, and an increase in divacancy concentration. Divacancies started to anneal above 1200 °C. Measurements between 8 and 293 K indicated that vacancies were neutral before as well as after annealing at 1380 °C. Fz-grown Si from one of these materials contained vacancy clusters with an average size of six to ten vacancies which persisted to 1380 °C. The cluster concentration corresponded to a monovacancy concentration of 10¹⁵ to 10¹⁶ cm⁻³, which is at least one order of magnitude larger than estimates based on voids [R. Falster, V.V. Voronko, F. Quast, Phys. Status Solidi B 222, 219 (2000)].