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^∘{}K 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^∘{}K 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).