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

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 T d 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 (2s 1 ,1s 1 ) 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.