The problem of conductivity-type inversion in wide band gap II-VI compounds

Abstract

To solve the problem of conductivity-type inversion in wide band gap II-VI compounds the thermodynamical analysis of intrinsic point defects has been performed. The existence of certain critical temperature of heat treatment in equilibrium conditions is shown. Above this temperature it is impossible to obtain the samples with stoichiometry deviation toward non-metals. At the temperatures lower than T c , the diffusion processes in crystals are retarded and the equilibrium between II-VI crystals and B component vapour cannot be established (B is a component of a binary compound AB). Thus, it is shown that under thermodynamical equilibrium conditions it is impossible to obtain wide band gap II-VI compounds of p-type conductivity.

ZnO: From basics towards applications

“…Look et al [61], there were recently reliable reports on p-type doping in ZnO with N, As or P, see, e.g. [61]. The nitrogen acceptor has, with about 100 meV, possibly even a smaller ionization energy than the standard acceptor Mg in GaN:Mg with 160 meV.…”

“…After a lot of poorly reproducible results and other problems summarized beautifully by, e.g. Look et al [61], there were recently reliable reports on p-type doping in ZnO with N, As or P, see, e.g. [61].…”

“…Indeed Li, Na, K, and also the I b elements Cu and Ag are known to form acceptors. However, they usually form deep acceptors with ionization energies around a few hundred meV [60,61], i.e. much larger than k B T at room temperature.…”

“…by using either two different acceptors simultaneously like ZnO:N,As or ZnO:Li,N or by combining even a moderate concentration of donors with a higher concentration of acceptors, e.g. in ZnO:Ga,N [61]. Furthermore, it has been claimed that Li may form a complex in ZnO with a relatively low ionization energy of 130 meV [62], which in turn provides an argument to assign the deepest bound-exciton complexes like I 10 again to acceptor bound-exciton complexes (see Section 9.2).…”

The regulation of defect concentrations by means of separation layer in wide-band II-VI compounds

“…The thermodynamic analysis of intrinsic defects in an AB(crystal)-B 2 (gas) system has shown [3] that the formation of intrinsic-defect p-type conductivity is possible at certain values of pressure and temperature. According to the same analysis the inversion of conductivity type is not expected above the so-called critical temperature (T cr ).…”