Donor ionization energy

Optical absorption measurements give band-gap data for cubic sihcon carbide as 2.2 eV and for the a-form as 2.86 eV at 300 K (55). In the region of low absorption coefficients, optical transitions are indirect whereas direct transitions predominate for quantum energies above 6 eV. The electron affinity is about 4 eV. The electronic bonding in sihcon carbide is considered to be predominantiy covalent in nature, but with some ionic character (55). In a Raman scattering study of vahey-orbit transitions in 6H-sihcon carbide, three electron transitions were observed, one for each of the inequivalent nitrogen donor sites in the sihcon carbide lattice (56). The donor ionization energy for the three sites had values of 0.105, 0.140, and 0.143 eV (57). 

Using Eq. (10) with z — 8.75 and m — 0.28m [10] for ZnO, the donor ionization energy for an electron is obtained to be 0.050 eV. The value of the donor ionization energy for an electron is about one third of the value for the hole, proportional to The experimental donor ionization energies of the... 

We have to make a comparison of the donor ionization energies between the experimental and calculated values, at least, for the monovalent substitutional impurities of group-IIIA elements at the host Zn site. It is, however, difficult due to a lack of detailed information of the experimentally obtained energy levels. 

A the acceptor electron affinity and I donor ionization energy. When z = 0, the molecules are neutral overall, but E and EpQ arises from the charge variations within the molecules. These are both small, and we neglect them for simplicity. Moreover, we suppose that Ey yy and E,.R depend only weakly on z. Consequently, we have that... 

The differenee between the donor ionization energy and the acceptor eleetron affinity is a decisive criterion for the exciplex formation. If this difference is too small, ground-state charge transfer (CT) complexes are formed. Electronie energy transfer via exciplexes probably play an important role in the photo-deeomposition of polymer hydroperoxide groups (POOH) sensitized by the carbonyl groups (CO) (cf. section 2.5). 

Figure 2.10 A plot of the electron concentration in a piece of silicon doped with 10 cm donor atoms having an ionization energy of 0.04 eV. The steep slope at high temperature (low inverse temperature) corresponds to the intrinsic behavior for carriers crossing the energy gap. The lower temperature behavior occurs in the presence of the 10 cm electron donors. The slopes of the two curves correspond to the 1.1 eV energy gap and the 0.04 eV donor ionization energies, respectively.

---