engleski

Common origin of doping-limiting mechanisms in IIB-VI compounds and alloys

Wide-band-gap II-VI semiconductors have a potential for a variety of applications, which are hindered by the difficulties in achieving efficient doping at both n- and p-side (above 1018/cm3). The origin and even more the microscopic nature of doping problems, remain controversial. The main causes are claimed to be either compensation by the spontaneously formed native defects and/or pairs, lattice relaxation around doping atom resulting in a formation of compensating deep localized levels, mid-gap pinning of the Fermi level, amphoteric behavior of some dopants, or insufficient solubility of others. We have shown that the common origin of all these different doping-limiting mechanisms can be traced down to the ratio of covalent radii of the constituent atoms (and respective vacancies) in the particular IIB-VI compound or alloy. This ratio then determines the ratio of vacancy formation energies, and finally the ratio of their relative concentrations. The practical consequence is that the n- and p-type dopability of IIB-VI compounds as well as their ternary alloys can be predicted in a simple way. Limits of the approach are discussed.

doping; II-VI; p-type; n-type; compensation; A center; DX center

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