A genuine neutral double acceptor in a II-VI semiconductor-SiTe(?) in ZnTe

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Abstract
The authors report the first clearly identified neutral double acceptor in any II-VI semiconductor, observed in Zn-annealed ZnTe. Optical properties of the associated bound exciton (BE) clearly identify the number of holes present in the exciton and the acceptor ground state and establish Td site symmetry. Zeeman and uniaxial stress perturbation spectroscopies were both required to establish the character of the double acceptor ground state in which the crystal-field ( Gamma 3- Gamma 5) splitting of the J=2 hole-hole state ( approximately 4.8 meV) is unexpectedly large compared to the J=0-J=2 splitting, ( approximately 0.9 meV), so that the Gamma 3(J=2) state of the neutral double acceptor lies lowest and is approximately 2 meV below the Gamma 1(J=0) state. A fourfold splitting is seen in the (2s1,1s1) excited state of the double acceptor when this is observed in the satellites of the main BE line. This is attributed to the presence of states with J=0, 1, 2 and 3 due to the coupling of the spins of the two holes, although residual crystal-field splittings may also be significant.