Germanium ionization energy

Table 5.3 Donor and acceptor ionization energies in silieon and germanium...

Look at their positions in the periodic table. The group 4A element germanium has four valence-shell electrons and thus has four relatively low ionization energies, whereas the group 5A element arsenic has five valence-shell electrons and has five low ionization energies. 

The group 4A elements exemplify the increase in metallic character down a group in the periodic table Carbon is a nonmetal silicon and germanium are semimetals and tin and lead are metals. The usual periodic trends in atomic size, ionization energy, and electronegativity are evident in the data of Table 19.4. 

There are cases where, in absorption measurements, the sample itself can be used as an extrinsic photoconductor, once provided with electrical contacts. This is illustrated in the specific case of germanium co-doped with acceptor couples (Ga, Zn), (Zn, Cu) and (Cu, Hg). The ionization energy of Ga is 11.3 meV, and those of the double acceptors, when neutral, are 32.9 meV (Zn), 43.2 meV (Cu) and 91.6meV (Hg). The continuous photoconductivity... 

As in silicon, for group-V donors in germanium, the photoionization cross-section at LHeT is maximum just above the ionization energy, but it is larger in units of 10 Mcm2, it is given as 1.8, 1.5, and 1.1 for Sb, P, and As, respectively ([21], and references therein). 

An evoked possibility of n-type doping of diamond with sulphur [219] has aroused an interest for the electronic properties of this element in diamond. It is now well established that, as expected from the properties of chalcogens in silicon and germanium, S behaves in diamond as a deep donor, with an ionization energy of 1 eV for S°, predicted from the ab initio DFT calculations [177]. However, the existence of S-related complexes with native defects or impurities like B is a possibility which could explain some appealing experimental results ([37], and references therein). 

In germanium samples diffused with TMs or Cu-contaminated, SAi-like acceptor spectra were also observed [23,71], These acceptors are also characterized by a split ground state. The ionization energies of their ground and thermalized states are given below, with SAi for comparison ... 

Table 7.15. Low-resolution positions (meV) of lines of the neutral groupll acceptors and of Cu° in germanium near 7K. When given, the positions of the thermalized lines are the upper ones. The optical ionization energy reported for Au° is 0.21 eV [89]...

In a germanium sample from an As-doped crystal pulled in vacuo and contaminated with Cu, the PTIS spectrum of a CuX centre has been reported by Sirmain et al. [156]. Its first ionization energy is 10.05 meV and the ther-malized energy is 9.15 meV. Piezospectroscopic measurements indicate a C v symmetry and the dissociation conditions of this complex have led to the tentative attribution of CuX to a (Cus, As) acceptor complex, which should normally behave as a double acceptor. 

Fig. 7.22. Absorption of BeGa between 14.9 and 29.8 meV in a GaAs sample with [Be] = 2.3 x 1016 cm 3. The labelling is the same as for the acceptor lines in germanium. The broad feature near 140 cm 1 is due to the mylar window of the cryostat. The ionization energy of Be corresponds to 225cm-1 or 27.9 meV [109]. Copyright 1996 by the American Physical Society...

Piezospectroscopic results of residual B and A/ in germanium for stresses between 300 and 640 MPa along the <100> and < 111 > axes have been reported by Kazanskii et al. [77] using PTIS. They were able to determine directly the shift with stress T of the ionization energies E of these acceptors at 2K (see Fig. 8.24). 

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