Broad photoluminescence bands which were about 0.1eV in full-width at half-maximum, and had energies which ranged from 0.70 to 1.03eV, were shown to be a commonly observed feature of p-type B modulation-doped epilayers that were grown at low temperatures by means of molecular beam epitaxy. It was shown that the presence of a particular broad band was determined by a bias that was applied to the substrate during growth. This provided evidence that the deep photoluminescence bands were at least partly induced by ion bombardment during growth. In order to clarify their origin, the effect of hydrogenation, and of a magnetic field, upon the photoluminescence bands was studied. The results indicated the existence of at least 4 types of radiative center. An observed correlation between X-ray diffraction and photoluminescence measurements suggested that some of the broad bands could be related to macro-defects such as defect clusters. Optically detected cyclotron resonance techniques were used to specify the spatial location of the broad band-related defects in the structures. Information concerning the dependence of the electron mobility upon the growth conditions was also obtained by means of optically detected cyclotron resonance techniques. The active role which was played by B dopants in the formation of the defects that gave rise to the broad bands was clearly demonstrated by comparison with results from undoped Si epilayers which had been grown under similar conditions.

I.A.Buyanova, W.M.Chen, A.Henry, W.X.Ni, G.V.Hansson, B.Monemar: Physical Review B, 1995, 52[16], 12006-12