Annealing of some II-IV-V 2 crystals in the vapor of volatile constituents
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Annealing of some II-IV-V2 crystals in the vapor of volatile constituents Valeriy G.Voevodin, Olga V.Voevodina, Svetlana A.Bereznaya, Zoya V.Korotchenko Siberian Physico-Technical Institute 1 Revolution sq., 634050, Tomsk, Russia Nils C. Fernelius, Jonathan T. Goldstein, Melvin C. Ohmer Air Force Research Lab Wright-Patterson Air Force Base, Dayton Ohio, 45433-7707, USA ABSTRACT Experiments on annealing of CdGeAs2- , CdSnAs2- and ZnGeP2-crystals in the vapor of volatile constituents were carried out. Conductivity and Hall effect measurements were performed to characterize the modification of electrical properties, caused by the interaction of the crystal with the gas phase during annealing. Literature data and the results of the present work are discussed based on the results of a quasi-chemical analysis. This yielded that the results of annealing depends essentially on both the conditions of the experiment and the initial imperfection of the crystal. The most probable native structural defects becoming apparent under the annealing were the following: for CdSnAs2 - SnCd, VAs; for CdGeAs2 - VAs , VCd, CdGe, GeCd; for CdSiAs2 - SiAs, VAs ; for CdSiP2 - VCd, VP; for ZnGeP2 - ZnGe, GeZn, VZn, VP; and for ZnSnP2 - ZnSn, SnZn, VZn, VP.
INTRODUCTION There is great interest in the ternary compounds II-IV-V2 (especially CdGeAs2 and ZnGeP2) because of their unique properties, among them their use as NLO converters for mid IR range radiation [1,2]. The widespread practical use of these materials is limited by the presence of absorption bands in their transparency range. These absorption bands are linked to deep level native defects [3-6]. For successful suppression of the undesirable influences of these defects on the properties of the material, it is necessary to define their nature. So far there have not been solutions of this task acceptable to all. Experiments on the influence of annealing in the vapor of volatile components on semiconductor electrophysical parameters may be rather informative in this respect. In this work research of such kind applied to nCdSnAs2, n- and p-CdGeAs2 and p-ZnGeP2 was fulfilled by the method of "frozen reactions“. EXPERIMENTAL RESULTS In the case of n-CdSnAs2 the dependence of electron concentrations on vapor pressure appear as curves with a minimum, the depth and position of which on the time axis were defined by defect parameters of the initial sample. This completely agrees with [8]. As it was reported in [9, 10], the hole concentration increased in p-CdGeAs2 with the lapse of time under annealing in As-vapor and went to saturation at a level about p ~ 1017 cm-3 under annealing times ~ 150 hours. The electron concentration increased in n-CdGeAs2 with the lapse of time under annealing in Cd-vapor and went to saturation at a level about n ~ 1018 cm-3 under annealing times ~ 100 hours [9]. As to ZnGeP2, it was reported in the work [11] H6.28.1
that the hole concentration in the material increased with increase of phosphorus pressure during synthesis of the compound. According to data of ot
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