Optical Determination of the Symmetry of the Ground States of Group-V Donors in Silicon

Excitation lines from the doublet, 1s (E), and the triplet, 1s (T₁), states have been measured at temperatures 80, 59, and 30^ for P, As, and Sb donors in silicon. On the basis of the relative intensities of the lines with the same final state it is deduced that the 1s (E) state lies above the 1s (T₁) state for all three impurities investigated. At 30^ the 1s (T₁) 2p₀, 2p_ transitions for antimony impurity resolved into a doublet. Uniaxial stress measurements for P and Sb, with compression F parallel to 100 or 110 and with the electric vector E either parallel or perpendicular to F, indicate that the lines with 1s (T₁) as their initial state do not exhibit any splittings or shift in their energies. On the other hand, the lines with 1s (E) as their initial state exhibit splittings with dichroic features. Experimental observations of the number and the positions of the stress-induced components and their polarization characteristics are consistent with the ordering in which 1s (E) lies above 1s (T₁).