摘要:

The formation of palladium silicide phases by implantation of Si ions into evaporated‐palladium films on two different substrates (Si and SiO2) has been investigated. The amount and phase of silicide formed depend on the implantation temperature, substrate type, and the penetration of the ions relative to the substrate depth. Provided the ions do not penetrate to the substrate, it is found that Pd2Si is formed for both types of substrate, even at 150 °K. When the ions just reach the Pd/substrate interface, the sample temperature and substrate type become important. For the SiO2substrate, the amorphous alloy Pd4Si forms at low temperatures. With the Si substrate Pd2Si forms under all conditions and there is a large incorporation of silicon from the substrate into the palladium, to an extent dependent on the temperature. This effect is explained in terms of radiation‐enhanced diffusion, possibly assisted by dynamic cascade mixing. In the SiO2substrate case, oxygen is thought to play an important role in determining the formation of phases.

ISSN:0021-8979    

DOI:10.1063/1.325773

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Emission and capture rates describing the optical and thermal transitions at the ’’Cu‐red’’ center in ZnSe have been investigated using a modified photocapacitance technique. By keeping the depletion region of a Schottky diode constant during the measurements of transients highly compensated samples could be used, resulting in larger signals than previously possible. This permitted optical‐emission rates for both electrons and holes to be measured with higher accuracy and in a broader temperature region than in previous investigations. The capture cross section of electrons &sgr;nwas determined in the temperature range 77–200 K. &sgr;nincreases with decreasing temperature and has a value of 1.4×10−19cm2at 77 K.

ISSN:0021-8979    

DOI:10.1063/1.325774

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A systematic study has been made of the deep level introduced into GaAs1−xPxalloy material by S doping. Conclusive documentation of the linear relationship between S concentration and the deep‐level trap concentration is presented forx?0.4. The dynamic properties of this trap measured atx=0.38 show a temperature activation energy for emission and electron capture of 0.35 and 0.15±0.03 eV, respectively. It exhibits a very large hole‐capture cross section at a site occupied by an electron. A very sharp drop in the ability to populate the trap belowx=0.35 is consistent with the trap being energetically tied to theXband minimum and having a depth of 0.17 eV below this band minimum. The dependence of the thermal‐emission activation energy on alloy composition is ascribed to the necessity to capture electrons from the indirect minima belowx?0.4. Photoionization experiments indicate that a much greater photoenergy than the thermal energy is required to ionize an electron trapped at this site (1.1 compared to 0.17 eV). Electron capture followed by a large lattice relaxation is consistent with the data and the phenomenon of persistent photoconductivity at low temperature associated with the S center. The S center in GaAs1−xPxprovides an efficient nonradiative recombination path for minority carriers.

ISSN:0021-8979    

DOI:10.1063/1.325775

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The photoluminescence excitation spectra of AlxGa1−xP alloys withx=0–0.8 were measured at temperatures between 20 and 145 K. The crystals used in this study were prepared by slow cooling from the Ga‐rich Al‐Ga‐P solution. Two sharp lines,LandH, were observed at 2.305 and 2.314 eV at 80 K. TheHline is identified with theAline in GaP, which is due to the N isoelectronic impurity bound exciton. TheHline reduced drastically when a small amount of Al was added to the initial solution. This is because the presence of Al in the solution increases the difficulty of nitrogen being introduced into the crystal. The photon energy corresponding to theLline shows that this line is due to the donor bound exciton. The threshold point energyE0and theLline hardly change untilx=0.4; abovex=0.4 the energyE0begins to increase and theLline disappears. It is proposed that small clusters of GaP are formed in the AlxGa1−xP alloy because of a disordered arrangement of the group‐III atoms in the sublattice. The size of a cluster is thought to be larger than the exciton radius of 29 A˚ estimated by the hydrogenlike model.

ISSN:0021-8979    

DOI:10.1063/1.325721

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Amorphous Hf1−xNixand Hf1−xCoxalloys in the concentration range 0.2⩽x⩽0.9 were prepared by melt spinning. The crystallization behavior of these alloys was studied by means of differential scanning calorimetry and x‐ray diffraction. At least two new compounds in the Hf‐Ni system were observed to be formed upon crystallization of the amorphous alloys. The electrical resistivity (&rgr;) in the amorphous alloys and in crystalline HfNi5was studied in the range from 4.2 to 300 K. Negative temperature dependences of &rgr; were observed in several of the amorphous alloys, extending fromx=0.25 tox=0.65 in Hf1−xNix. The thermal stability of the amorphous alloys is discussed in terms of a diffusion mechanism. The extended Ziman theory of liquid metals was used in the interpretation of the temperature dependence of the resistivity.

ISSN:0021-8979    

DOI:10.1063/1.325724

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

It is shown in this study that photon recycling, i.e., photoluminescence resulting from the self‐absorption of photons generated by prior luminescence processes, affects the steady‐state characteristics of graded‐band‐gap Ga1−xAlxAs : Si LED’s strongly and of constant‐band‐gap GaAs : Si LED’s weakly. In Ga1−x Alx As : Si, where the internal quantum efficiency is near unity, photon recycling can enhance the external quantum efficiency (&eegr;ext) by 25% or more. Moreover, the effective minority‐carrier diffusion length (L) can be augmented by ∼40%. On the other hand, because the internal quantum efficiency in GaAs : Si is considerably less than 100%, the effect of photon recycling on &eegr; andLis less pronounced. A theoretical model of photon recycling in both the graded‐ and constant‐band‐gap material is formulated and its predictions for the effects on the external quantum efficiency, the diffusion length, and the electroluminescent spectrum are in good agreement with the experimental results.

ISSN:0021-8979    

DOI:10.1063/1.325725

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The thermoelectric power of polycrystalline double hexagonal‐close‐packed samples of Nd1−xLaxand Ce1−xLaxhas been measured from 2 to 300 K. Single crystals of Nd have also been measured. These results confirm that there are at least two magnetic‐transition temperatures in both sets of alloys. Data for Nd affirm there is a Ne´el temperature at 19.2 K and an incommensurate to commensurate transition at 7.5 K. These features are much less prominent in Ce and Nd thermopower data than corresponding features in the heavy rare earths. There is some anisotropy in the Nd single‐crystal data, but thea‐ andc‐axis data are similar in shape. In the Ce‐rich Ce‐La alloys there is a large positive peak at 75 K and a negative peak at ∼5 K.

ISSN:0021-8979    

DOI:10.1063/1.325726

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The electron trapping behavior of SiO2has been measured as a function of thickness at 295 and 77 °K. The devices used were metal‐oxide‐semiconductor devices with the SiO2grown thermally. The results indicate bulk traps are dominant at 295 °K and traps associated with the Si‐SiO2interface are dominant at 77 °K. The effect of processing conditions was also studied and the optimum conditions are different for the two temperatures used for the measurements. These observations have been verified using a photoI‐Vtechnique. The generation of donor states in the SiO2near the Si‐SiO2interface was observed as a result of the electron current through the SiO2.

ISSN:0021-8979    

DOI:10.1063/1.325727

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Details of a method for the characterization of deep levels with large capture cross sections for minority carriers are presented. This technique has been used to investigate centers in gallium phosphide. Two defects atEV+0.75 eV andEV+0.95 eV are described in detail. Evidence is presented that shows that the shallower of these defects can control the minority‐carrier lifetime inn‐type gallium phosphide and in fact is the dominant recombination center in most epitaxial layers of this material. The technique uses capacitance as a measure of the charge state of the deep levels in the depletion region of a Schottky barrier. This charge state is perturbed by the capture and subsequent thermal emission of minority carriers. The carriers are generated by irradiation of the semiconductor with low‐intensity light at a wavelength near the absorption edge. Minority carriers generated in the neutral material within about a diffusion length of the barrier region are extracted by the depletion field. Majority carriers are excluded by the field and consequently the current through the barrier is due predominantly to minority carriers. These are captured by the defects, the fastest capture being into the levels with the largest capture cross sections. As a result, the technique can in many cases be used selectively to detect the most important recombination centers in a semiconductor and to determine their capture cross sections, concentrations, and energy depths.

ISSN:0021-8979    

DOI:10.1063/1.325728

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The influence of ion‐irradiation damage on the electrical properties of Hg0.79Cd0.21Te has been investigated. A large damage‐inducedn‐type conductivity with sheet carrier concentration up to approximately 1014cm−2and sheet resistance up to 10 &OHgr;/square at 77 K was found for doses of 1×1015ions/cm2at 150 keV. The observedn‐type conductivity is produced by various implanted ions regardless of whether they are donors or acceptors. The implantedn‐type layer maintains its properties when subjected to temperatures as high as 120 °C. The damage is slightly annealed for this moderate treatment: the conductivity increases slightly, the sheet electron concentration decreases, and the effective mobility increases. The results also show that the implanted layer can be utilized for surface passivation ofn‐type photoconductors and for making Ohmic contacts ton‐type material.

ISSN:0021-8979    

DOI:10.1063/1.325729

出版商:AIP    

年代:1979

数据来源: AIP