The forbidden energy gaps of Ge, Si, normalGaAs , and normalGaP have been used to obtain the standard Gibbs energy, enthalpy and entropy of formation of electrons and holes for each semiconductor up to the melting points. The forbidden energy gap is the standard Gibbs energy of formation of electrons and holes and the enthalpy and entropy have been obtained from the energy gap as a function of temperature and familiar thermodynamic relationships. Energy gaps as a function of temperature, available in the literature, have been fit to the semiempirical equation of Varshni and used to extrapolate the energy gaps and thereby the three thermodynamic functions to the melting points. It is well known that the energy gaps, i.e., the Gibbs energies, decrease with increasing temperature but it is not well known that the enthalpy of formation increases with temperature and that it is proportional to the slope of the familiar logarithmic plot of the intrinsic carrier concentration over T3/2 vs. 1/T . Examples of the utility of the enthalpy function are given. It is the entropy that leads to the decrease in energy gap with increasing temperature and its magnitude is large near the respective melting points (10–13 cals/deg, i.e., 4 normalto 5.6×10−4 normaleV/normaldeg ) arising from the interactions of electrons and holes with the lattice. The intrinsic carrier concentrations were calculated from the forbidden energy gaps and the average effective masses which were estimated for the higher temperatures.

New measurements are reported on the solubility of germanium in liquid gallium, thallium, tin, arsenic, bismuth, cadmium and zinc, and the solubility of silicon in liquid indium, tin, lead, antimony, bismuth and zinc. The measurements of other workers are reviewed, including those of the solubility of germanium and silicon in liquid copper, silver, gold and aluminum; of germanium in liquid indium, lead and antimony; and of silicon in liquid arsenic and nickel. All but two of the liquidus curves can be described within experimental error by a two‐constant equation. The form of this equation suggests that the liquid solutions exhibit certain simple thermodynamic properties, and some evidence is cited indicating that the constants of this equation can be used to estimate the excess free energy of the solutions. Figures for the complete liquidus curves of these binary systems (T—x and log x–1/T) have not been included in this paper, but sets of these figures can be supplied upon request.

We have grown and measured the optical second-harmonic coefficient dijk of the new nonlinear crystal 2-methyl-4-nitroaniline (MNA). We find that the dijk are very large with d12 being 5.8 times larger than d31 of LiNbO3 giving a birefringence phase-matching figure of merit d2/n3 which is 45 times larger than LiNbO3. The other coefficient d11 is 40 times larger than LiNbO3, giving a huge figure of merit which is 2000 larger than LiNbO3.

%'e make simple estimates of the entropy of ionization of Coulombic, isoelectronic, and vacancy-type defects in semiconductors by considering the effect of localized and free-carrier charge distributions upon the lattice modes. The empirical values of these entropies are observed as the temperature variation of the corresponding ionization levels. %'e predict a crossing of vacancy donor and acceptor levels in Si and Ge, which is supported by quenching and diffusion experiments. %e also conclude that some of the deep Coulombic defects, such as the Au acceptor in Si, are most likely a complex of the Coulombic center with some isoelectronic or vacancy defect, such as Au interstitial with Si vacancy, rather than a simple substitutional impurity as previously assumed.

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