J. Phys. III France 1 (1991) 1481-1487
On quantitative mapping of EL2 concentration in semi-insulating GaAs wafersU. V. Desnica1, B. G. Petrovic1, M. Skowronski2 and M. C. Cretella2
1 R. Boskovic Institute, P.O. Box 1016, 41001 Zagreb, Yugoslavia
2 Cabot Corp. Concord Road, Billerica, MA 01821, U.S.A.
(Received 18 March 1991, revised 21 May 1991, accepted 3 June 1991)
Different factors influencing the accuracy of quantitative EL2 mapping were analyzed. It was found that very often the main problem limiting precision of those measurements is fluctuations in the transmitted light due to surface, subsurface and volume imperfections of the wafer. This problem was solved by combining results of 2 sets of 2-dimensional scans taken at two different light energies ; one at 1.1 eV giving information on EL2° absorption, and the other, below 0.8 eV, giving the background transmissivity. It is shown that this low-energy light mapping of GaAs wafer can also be used for evaluation of GaAs wafer preparation techniques.
© Les Editions de Physique 1991