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Undoped and Fe-doped liquid encapsulated Czochralski (LEC) InP has been studied by Hall effect, current-voltage (I-V), and infrared absorption (IR) spectroscopy. The results indicate that a native hydrogen vacancy complex donor defect exists in as-grown LEC InP. By studying the IR results, it is found that the concentration of this donor defect in Fe-doped InP is much higher than that in undoped InP. This result is consistent with the observation that a much higher concentration of Fe[sup 2+] than the apparent net donor concentration is needed to achieve the semi-insulating (SI) property in InP. By studying the I-V and IR results of Fe-doped InP wafers sliced from different positions on an ingot, the high concentration of Fe[sup 2+] is found to correlate with the existence of this hydrogen complex. The concentration of this donor defect is high in wafers from the top of an ingot. Correspondingly, a higher concentration of Fe[sup 2+] can be detected in these wafers. These results reveal the influence of the complex defect on the compensation and uniformity of Fe-doped SI InP materials. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The exchange bias effect has been observed in the superlattices consisting of ferromagnetic La0.67Sr0.33MnO3 and nonmagnetic insulating SrTiO3 layers. It is found that the exchange field shows an oscillatory decay with a period of ∼12 unit cells and approaches to a constant value of -100 Oe when the SrTiO3 thickness is increased. The tunneling current also displays a nonmonotonic decrease with the SrTiO3 thickness. These observations can be discussed on the basis of the interlayer exchange coupling between La0.67Sr0.33MnO3 layers via the spin-polarized electrons tunneling across the SrTiO3 spacers. [ABSTRACT FROM AUTHOR]

The authors report the formation of the metallic oxide p-I-n junctions with the ferroelectric (Ba,Sr)TiO3 (BST) as the barrier. The junctions with different thicknesses of BST are investigated. With appropriate thickness, the junctions possess definite parameters, such as the negligible reversed current density (<=10-7 A/cm2), large breakdown voltage (>7 V), and ultrahigh rectification (>2×104) in the bias voltage ≤=2.0 V and temperature range from 5 to 300 K. It is under consideration that the built-in field V0, the ferroelectric reversed polarized field Vrp, and the resistivity of the BST layer together decide the transport properties of the junctions [ABSTRACT FROM AUTHOR]