Defect interactions of group-I elements in cubic II-VI compounds

Abstract

By means of perturbed ␥␥ angular correlation ͑PAC͒ experiments using the radioactive dopants 77 Br, 111 Ag, and 111 In, the behavior of the group-I elements Li, Cu, Ag, and Au is investigated. Group-I elements are shown to form nearest-͑NN͒ and next-nearest-neighbor donor-acceptor pairs in the II-VI semiconductor CdTe. The simultaneous occurrence of cation vacancies indicates the transition of group-I elements from substitutional to interstitial lattice sites. In case of NN pairs, the electric-field gradients measured in the PAC experiments are compared with those obtained theoretically by density-functional theory calculations. PAC experiments performed in ZnTe and ZnSe show a similar behavior regarding the donor-acceptor pairing with group-I elements in these compounds.

The Potential of the Perturbed Angular Correlation Technique in Characterizing Semiconductors

“…The formation of similar defect complexes was also observed in II-VI semiconductors CdTe, ZnTe, ZnSe, and Hg 1Àx Cd x Te. 13,14 The lattice site locations of implanted 111 In in a GaN lattice was studied by PAC spectroscopy. 15 Using 77 Br as probe, the metastable behavior of anion-site donors in an InAs lattice was observed 16 where the transition between the substitutional and a nonsubstitutional configuration could be detected.…”

“…This sensitivity is advantageous for discriminating the presence of intrinsic and extrinsic defects in semiconductors, which is in general a basic problem in defect studies. Extensive PAC data are available on such measurements in semiconductors, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] which can be summarized as follows:…”

Experimental Verification of Calculated Lattice Relaxations Around Impurities in CdTE

“…The next-nearest neighbor shell was included with a fixed value taken from the pure system. The occurrence of various configurations which we experience here may also explain the relatively small fraction with which the PAC experiment detected the 111 Ag-Br pair [2].…”

“…In the case of As and Br in CdTe acting as acceptor and donor, resp., when incorporated substitionally on the Te sublattice, information on lattice relaxation around the impurity atom has already been obtained by hyperfine interaction studies. Making use of the donor-acceptor-pair formation between In-As and Ag-Br the electric field gradient (EFG) was determined for the non-cubic configuration with the resulting pairs of 111 Cd-As [1] and 111 Cd-Br [2] after the decay of 111 In or 111 Ag, resp., employing the perturbed angular correlation (PAC) technique. In ab initio calculations using density functional theory (DFT) as implemented in the WIEN97 program the EFGs were reproduced when the lattice distances around the impurity atom were first allowed to relax to minimize the forces within the super-cell [1,3].…”

Experimental Verification of Calculated Lattice Relaxations Around Impurities in CdTe

“…In the case of As and Br in CdTe acting as acceptor and donor, resp., when incorporated substitionally on the Te sublattice, information on lattice relaxation around the impurity atom has already been obtained by hyperfine interaction studies. Making use of the donor-acceptor-pair formation between In-As and Ag-Br the electric field gradient (EFG) was determined for the non-cubic configuration with the resulting pairs of 111 Cd-As [1] and 111 Cd-Br [2] after the decay of 111 In…”