Semiconductor Physics, Quantum Electronics & Optoelectronics. 2008. V. 11, N 1. P. 040-042.


Self-purification effect in CdTe:Gd crystals
E.S. Nikonyuk1, V.L.Shlyakhovyi1, M.O. Kovalets1, M.I. Kuchma1, Z.I. Zakharuk2, A.I. Savchuk2, I.M. Yuriychuk2

1National University of Water Management and Conservation, 11, Soborna str., 35011 Rivne, Ukraine; phone(0362)230420; e-mail: semirivne@mail.ru
2Chernivtsi National University, 2, Kotsyubynsky str., 58012 Chernivtsi, Ukraine Phone (0372)584875; e-mail: microel@chnu.cv.ua

Abstract. The temperature dependences (T = 80 – 420 K) of the concentration of charge carriers and the Hall mobility in undoped CdTe and CdTe:Gd single crystals grown by the Bridgman method are studied. It is found that the conductivity type of CdTe:Gd crystals changes with increase in the impurity concentration in the melt: n-conductivity at 5.10 17 – 3.10 18 cm –3 and p-conductivity at 3.10 18 – 10 19 cm –3 . The concentrations and ionization energies of A 1 (E A1 = 0.05 eV) and A 2 (E A2 = 0.12-0.15 eV) acceptors are determined from the temperature dependences of the Hall coefficient and the mobility of carriers. A long-term thermal treatment of gadolinium-doped p-CdTe crystals in the range 663 – 713 K is accompanied by the “self-purification” of the material from A 2 - acceptors and compensating donors. The Gd impurity at C 0 > 3.10 18 cm –3 is shown to bring no new electrical active centers into the CdTe lattice, by reducing, at the same time, the background of residual impurities. It is suggested that Te precipitates and Te inclu- sions serve as sinks for the above defects.

Keywords: semiconductors, cadmium telluride, doping, electron conduction, Hall effect.

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