The A Charge State

Good-quality spectra of Zn- in germanium have been reported by Piao et al. [138], The line positions of Be- are given in Table7.16 and compared with the calculations of Fiorentini and Baldereschi [58]. 

Sb-doped germanium samples diffused with copper show absorption thresholds at 0.32 eV in the near IR which can be associated with the onset of the 

For shallow multiple acceptors associated with the Fs+VB, the fourfold degeneracy allows one to accommodate a maximum of four holes. Photoconductivity measurements in the very-far IR at LHeT and down to 1.2 K have indeed shown that group-II neutral acceptors and Cu° could bind an extra 

In this section are presented results on Au, a group-IB element, and on the group-II acceptors. The results on Pt and Mn, two transitions metals whose spectrum bears resemblance with that of Au, are also presented. 

The behaviour of group-II FAs in silicon is interesting. Mg behaves as an interstitial double donor and Zn as a substitutional double acceptor. Be shows an acceptor behaviour, but it has been stated that only T0% of the Be concentration in silicon is electrically active (quoted by Crouch et al. [45]). Discrete acceptor spectra have been reported at LHeT in Be- and Zn-doped silicon and they include many complexes. In the case of Be, EM acceptor-like spectra associated with four different centres have been reported [45,99]. They are sometimes denoted in the literature Be-I, Be-II, Be-III, and Be-IV, with ionization energies of 192, 146, 200, and 93meV, respectively. Spectra due to (Be, Lij) pairs have also been reported [45,137]. Only the first low-energy lines of these spectra are observed, but the line spacings are comparable to those observed for the group-III p3/2 spectra. Some of the p1/2 spectra associated with these centres have also been observed [99,137]. 

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