Solubility Interactions in Compensated, Heavily Doped Germanium

The solubility of the two donors, arsenic and antimony, in Ge at 870°C was enhanced by the acceptor dopant Ga at concentrations ≥ 10^19 cm^–3. The observed enhancement is in agreement with theory of the dopant-carrier ionization equilibrium in the Boltzmann approximation and confirms the requirement of the theory that the solubility enhancement depend only on the net carrier concentration and not on the chemical identity of the donor. A contrary result would have been likely, if donor-acceptor complexes played an important role in these solubility effects. The experimentally determined intrinsic carrier concentration at 870°C is ni = 1.8 × 10^19 cm^–3 compared to the extrapolated Hall value of ni ~1.3 × 10^19 cm^–3. The indicated extrinsic behavior implies that p-n junctions persist in very heavily doped germanium to the melting point

Interaction between Arsenic and Aluminum in Germanium

The behavior of As in Ge containing regions doped with ∼5×10^20∕cc Al was studied. The solubility of As is enhanced tenfold or more by the heavy Al doping, on the basis of (1) measurements of conductivity type and (2) the negative results of a search for compounds by x‐ray diffraction. The behavior of As diffusion fronts was studied by observing the progress of the p‐n junction formed in Ge containing 10^(17)∕cc In. When a region of heavy Al doping was added, the p‐n junction was displaced. The displacements indicate that the diffusing As is attracted to regions of heavy Al doping. These results are similar to those of Reiss, Fuller, and others for Li in Si, though a detailed understanding is not yet available in the present case

Influence of Arsenic Pressure on the Doping of Gallium Arsenide with Germanium

THE doping of III-V compounds with elements from the IVth column of the periodic table has been studied under standard conditions of preparation by several investigators. In most cases, the IV element was found to act as an n-type dopant of low doping efficiency, a result that is usually interpreted to mean that more of the impurity atoms are located on the III element sublattice than on the V element sublattice. Causes for the unequal distribution of impurity atoms between the two sublattices have been sought in the sizes of the atoms and in their binding energies. An additional influence on the impurity atom distribution, namely, the vapor pressure of the V element, is considered in this note. A simple estimate will be given of the magnitude expected for the pressure effect, followed by some qualitative results for Ge-doped GaAs

Donor behavior in indium-alloyed silicon

The anomalous doping behavior of Si regrown from In solution was studied by (1) Schottky barrier evaluation of conductivity type, (2) electron microprobe analysis for phosphorus, and (3) channeling effect measurements for interstitial In. The latter showed In present at ~ 10^19 cm^–3, but not occupying a regular substitutional or interstitial position. A correlation was found in the first two measurements between phosphorus contamination and n-type conductivity. When the In was contacted only by quartz freshly etched in HF, the n-type behavior and phosphorus contamination disappeared. The anomalous doping behavior is most likely due to phosphorus inpurity picked up by the In

Diffusivity and Solubility of Si in the Al Metallization of Integrated Circuits

Si was diffused along the evaporated Al layer of an integrated-circuit structure at temperatures between 360 and 560 °C, and the resulting concentration profile analyzed by electron microprobe. The Si solubility was found to agree with literature values for Si in wrought Al. The Si diffusivity was found to be substantially enhanced, however, probably due to a high density of imperfections in the evaporated Al film. Our measured diffusivities indicate an activation energy EA ~= 0. 8 eV, about 40% less than the value for Si in wrought Al

Precipitation of Si from the Al metallization of integrated circuits

The Al metallization of integrated circuits is known to dissolve 1/2% or more Si, but the ultimate location of this Si has been uncertain. An electron microprobe operated at low beam energy so as to penetrate only the upper portion of the metallization was used to follow the movement of dissolved Si on cooling after the "forming" heat treatment. Dissolved Si substantially less than a diffusion length from the substrate was found to regrow there; elsewhere the Si forms precipitates in the Al matrix, preferentially near the free surface of the Al

The metal-semiconductor interface

Interfaces between metal and semiconductor may be found almost everywhere in contemporary electronics. Often the metal is there just to serve as a contact to p-n junctions in the semiconductor. At other times, the metal-semiconductor interface itself performs essential electronic functions. Considerable scientific interest has been devoted to this latter situation since early in the century, as discussed by Welker (1) in the previous volume of this series. This early work led to a rather simple and classical model, in which an electrostatic barrier o arises within the semiconductor and produces the rectifying behavior. The barrier o is called the Schottky barrier or Schottky-Mott barrier in remembrance of that work. The prediction of o has proven not to be so simple, however, whether in terms of other phenomena (such as work functions) or terms of fundamental theories. It is to the various contemporary aspects of this problem that the present review is principally devoted