Single-crystal platelets (3×3×0.1 mm) of both tetragonal and orthorhombic lead oxide have been grown from dilute NaOH solutions at high pressures using conventional hydrothermal techniques. The predominant yield of the two phases was varied in accord with the P-T phase diagram of PbO. Electrical measurements include the Hall coefficient and electrical conductivity as a function of temperature, while the corresponding photoeffects and optical absorption with monochromatic radiation were also studied. ``As-grown'' tetragonal crystals were highly conducting n-type with σ(300°K) ∼10−3 to 1.0Ω−1 cm−1, and had Hall mobilities of about 100 cm2V−1 sec−1. In constrast the ``as-grown'' orthorhombic crystals were rather insulating with σ(300°K) ∼10−5Ω−1 cm−1 and a Hall mobility μe∼50 cm2V−1 sec−1. Heat treatment in air altered both the electrical and optical properties. Photoconductivity was observed in both crystalline forms. The optical measurements indicate band transitions at 1.90 eV and 2.75 eV for the tetragonal form and 2.67 eV for the orthorhombic modification.
Gallium phosphide has been grown epitaxially by open tube vapor transport using Ga and PCI3 as starting materials. The over-all reaction for the process can be represented by 5Ga ~-2PC13 ~ 2GaP + 3GaC12. The undoped GaP obtained is p-type with carrier concentration ,-,1014 cm -3 and mobilities up to 150 cm 2 v -1 sec -1 at 300~ The transport properties as well as the mass spectroscopic analysis are presented and demonstrate the high purity of the GaP. The addition of water vapor to the hydrogen carrier gas progressively raises the resistivity of the p-type epitaxial layer. Semi-insulating GaP has been produced by this method with resistivities over 10 TM ohm cm.
A correlation between photoconductive and photo-Hall data on GaP has revealed direct evidence of hole trapping. From these same data, the position of the sensitizing centers was determined to be 0.66 eV above the valence band. Also, electron to hole mobility ratios between 1.1 and 1.3 and lifetimes of photogenerated carriers in the high-light region of ~6X10-e sec were calculated.The effect of edge dislocations on electrical noise in n-type silicon has been investigated. Parallel arrays of edge dislocations have been introduced by plastic deformation in vacuum at near 950°C, and the amount of dislocations introduced has been examined by etch pits. Electrical conductivity and noise measurements confirm the Shockley-Read model, according to which edge dislocations behave as lines of acceptors in semiconductors with the diamond structure. From the conductivity measurements, values of the fractional disturbed volume, E, of the concuctive sample are deduced in accordance with Read's theory. Noise results in dislocated samples show 1/j and g-r components differing from those of control samples obtained from the same ingot and also differing from samples subjected to the same heat treatment but without introduced dislocations. The g-r noise can be explained in terms of fluctuations in E, which in turn are caused by fluctuations in the number of captured electrons at the dislocation sites. It is found that, in the temperature range 25°-170°C, for 200-a·cm samples, the observed time constants and noise amplitudes are consistent with fluctuation phenomena associated with the dislocation sites acting as recombination centers. However, at near and below room temperature, trapping at the dislocation sites seems to be the primary cause of the observed noise behavior.
Coevaporation with vapor quenching has been used to combine metallic and nonmetallic elem.ents into new vitreous semiconductors. These binary glasses, formed with an excess of nonmetal over. a wide ran.ge of compositions exhibit semiconducting and optical properties differing from the correspondmg proper~Ies of either component alone or of any known crystalline compound formed between the comp.onents. Detal~e? investigation of the vitreous Bi-Se system indicates that an inten;ne?iate temperature :el?~n of the equilibrium phase diagram has been retained at room temperatU1:e. VanatIon of ban~¥aI?' resls~lv~ty, and phootosensitivity with composition are presented and interpreted m tenns of the eqUilibnum eXlstmg at ",620 C.
The infrared photodetecting properties of new vitreous Bi–Se films are described. Such films are prepared by coevaporation and vapor quenching. A room-temperature D* value of 2×1011 cm/W·sec1/2 was measured at the peak sensitivity wavelength (∼1 μ) for an optimum composition film. Response times range between 0.3 and 3 msec. In addition, measurements were made of D* as a function of sample composition, incident photon flux, and temperature.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.