COMMENTS ON THE DETERMINATION AND ANALYSIS OF OPTICAL CONSTANTS OF THIN SILICON FILMS.

Amorphous and crystalline pure silicon films have been analysed by optical transmission spectroscopy and the optical constants determined in the region of the fundamental absorption edge. It is shown that it is intrinsically difficult to ascertain the 'true nature' of the absorption edge because of the large relative uncertainty in the measurement of alpha for values of alpha less than about 500 cm** minus **1. From analysis of the region where alpha is greater than 500 cm** minus **1, it is shown that relatively void free amorphous silicon films can be prepared which possess the same optical band gap as crystalline films with an increased density of states near the band edges.