It was recalled that, when this material was made p-type by the incorporation of N, a compensation process occurred at effective acceptor concentrations of between 1017 and 1018/cm3. This was due to the creation of compensating donors which were thought to lie at a depth of about 0.045eV. It had previously been deduced, from optically detected magnetic resonance and spin-flip Raman-scattering data, that these donors had a g-value of about 1.4; as compared with the g-value of 1.1 for the more usual shallow donors which lay at about 0.026eV. A systematic study was made here of a series of molecular beam epitaxial layers in which the N concentration was gradually increased. This confirmed a correlation between the onset of compensation, at an effective acceptor concentration of about 1.7 x 1017/cm3, and the appearance of the 0.045eV donor. It was noted that spin-flip Raman scattering was a resonance process that required the laser energy to coincide with the excitonic transition that was associated with the donor, and this effect was exploited in order to determine the difference in the localization energies of excitons that were bound at the 2 types of donor. The results showed that Haynes’ rule was obeyed for donor depths of at least 0.045eV.

C.M.Townsley, J.J.Davies, D.Wolverson, P.J.Boyce, G.Horsburgh, T.A.Steele, K.A.Prior, B.C.Cavenett: Physical Review B, 1996, 53[16], 10983-7