A method for growth of single-crystal silicon doped heavily, with thallium has been developed to make use of the good match of the thallium acceptor cutoff wavelength (5.0μ) to the 3-5μ atmospheric window. The method involves recrystallization of silicon from a tin-thallium solution kept saturated by a silicon source wafer. Growth conditions used success fully to date range from 1100°C to 1370°C in growth temperature, and from 7% to 50% tin fraction in the tin-thallium solvent. The thallium doping increases monotonically with increas, ing growth temperature or thallium fraction in the solvent. A model of the dependence of the thallium doping on temperature and solvent composition is presented, as well as the estimated solubility limit of thallium in silicon. The most heavily doped crystal was grown at 1370°C from a Sn.14T1.86 solvent, and produced a maximum photoionization absorption of 2cm-1 at 3μ. This corresponds to a predicted quantum efficiency of 18% in a 1-mm thick detector. The Hall mobility of the grown material near liquid nitrogen temperature is found to approach 2000cm2/V-sec.

Date Published: 11 June 1981
PDF: 7 pages
Proc. SPIE 0285, Infrared Detector Materials, (11 June 1981); doi: 10.1117/12.965807

Published in SPIE Proceedings Vol. 0285:
Infrared Detector Materials
H. R. Riedl, Editor(s)