Electron Beam Induced Current Images Research Articles

Analysis of electrical properties of amorphous silicon films in distinct local environments by the ebic method

It has been confirmed that the Electron Beam Induced Current (EBIC) technique is effective for the investigation of amorphous Si (a-Si) properties. Appling the EBIC method to an analysis of a-Si properties, it is possible to investigate the fine property distribution with two-dimensional information at a distinct local environment. EBIC images of a-Si films on various kinds of substrates were obtained with the limit of the resolution being about 0.5 μm. The fine property distribution indicated by the EBIC image corresponds well with the unevenness of the surface of a-Si films. Therefore, it has been possible to carry out a morphological study and a property investigation of a-Si films by the EBIC technique.

The temperature dependence of EBIC contrast from defects

The Electron Beam Induced Current (EBIC) mode of the SEM has been extensively used to reveal the presence of electrically active dislocations in semiconductor specimens. Only in recent years, however, have attempts been made to deduce quantitative information from this technique and relate such information to the details of the recombination process at individual defects. A major advantage of the EBIC technique is its high spatial resolution and thus its ability to yield electrical data from individual extended defects.Fig. 1(a) is a TEM micrograph of a widely dissociated screw dislocation, obtained with a forbidden reflection of the type 1/3 (422), where the stacking fault ribbon between the 30° partials is showing bright constrast. Fig. 1(b) is a corresponding EBIC image, where the individual 30° partials are directly resolved for the first time. Since the ultimate resolution of an electrical technique is essentially determined by the Debye screening length, which in the sample of Fig. 1 is approximately 0.1μm, it is clear that EBIC is capable of approaching this resolution limit.

EBIC characterization of recrystallized HgCdTe

Electron beam induced current (EBIC) images of skin junctions formed during postannealing in excess Hg have been used to study recrystallized HgCdTe. The skin junction has been found to be nonplanar, and variations in its position are consistent with the dissolution of second‐phase Te. EBIC images have demonstrated enhance diffusion of Hg along grain boundaries, in addition to suggesting that these boundary regions can be electrically active as carrier generation centers. Dislocation subgrain boundaries, which have also been observed, appear to be active as recombination centers.

Strain-related degradation phenomena in long-lived GaAlAs stripe lasers

Qualified GaAlAs/GaAs oxide isolated stripe geometry DH lasers, degraded at temperatures up to 90 °C, have been examined using the cathodoluminescence (CL) and electron beam induced current (EBIC) modes of the scanning electron microscope, and by transmission electron microscopy in a 1-MeV TEM. The main features observed in the EBIC and CL images in the plane of the heterojunction of the degraded lasers were bright and dark bands running parallel to the stripe, together with brightened mottled regions extending well outside. The separation of the bands and the extent of the mottled region is dependent on the width of the stripe. This general pattern is modified considerably near to the facets of the lasers. Calculations of strain profiles for the different laser types suggested that these phenomena can be explained in terms of a model of operation induced, strain enhanced, defect migration. Small dislocation loops seen at the edges of the stripe, using transmission electron microscopy appear to support this model.

Scanning Electron Microscopic Observation of Oxidation-Induced Stacking Faults in Silicon

An electron beam induced current (EBIC) method using an Al-Si Schottky barrier has been developed and applied to the observation of oxidation-induced stacking faults in (001) silicon. The minority carriers in thermally-oxidized silicon have a very large diffusion length. Analysis of the Y-modulation image of a stacking fault is effective for correlating the EBIC image contrast with the induced-current variation. Increasing beam energy increases the depth of a Frank partial dislocation segment showing the maximum contrast. A deep dislocation segment shows a larger resolution than a shallow one, and a further increase in resolution results from an increase in the beam energy. The Schottky barrier method is applied to the evaluation of the electrical activity of stacking faults and to the examination of their annealing behavior.

Computer simulation of SEM electron beam induced current images of dislocations and stacking faults

Images of dislocations and stacking faults as obtained in the scanning electron microscope operating in the electron beam induced current (EBIC) mode are produced by computer simulation on a cathode ray tube plotter. The calculations are based on a model describing charge-collection by a surface barrier in presence of a defect and assume that the minority-carrier diffusion length L in the bulk semiconductor is infinite. It is shown that the approximation L=∞ is valid when L≫Rp (Rp is the range of the electron beam) and is suitable for studying the EBIC images of defects in silicon. Simulations of dislocation images illustrate the influence of the inclination angle of a dislocation with respect to the surface on the shape of its EBIC image. Computed images of stacking faults in (100) and (111) Si are used to investigate the dependence of the contrast distribution of the image on the energy of the electron beam. Comparison with some experimental micrographs indicates that the model gives a satisfactory description of observed images. Limitations and possible improvements of the model are also discussed.

New STEM spectroscopic techniques for simultaneous electronic analysis and observation of defects in semiconductor materials and devices

The main interest in the study of defects in semiconductor materials lies in their electronic properties and their effects on the device characteristics. Conventional transmission electron microscopy (CTEM) and scanning transmission electron microscopy (STEM) provide the tools for analyzing the crystallographic nature of defects in these materials. However, until now, there have been no techniques which allow for the simultaneous observation of a defect along with an analysis of its electronic properties, e.g., energy level, radiative and nonradiative behavior. We have developed on a STEM unit several techniques which permit displaying and analyzing the spatial distribution of nonradiative and/or radiative recombination centers in a thin semiconductor sample which may be simultaneously analyzed by STEM and CTEM.The first technique uses the electron beam induced current (EBIC) in the thin sample which contains a p-n junction or a Schottky barrier. The surface recombination effects have been minimized to allow for high contrast EBIC images of the recombination centers in the material.

Scanning electron microscopy of charging effect on silicon

Charging effect induced by an analyzing electron beam of a SEM has been observed on the cleaved surface of a silicon wafer. It was ensured that this is due to the formation of an oxide layer on the silicon surface. Using this effect, two new applications of the electron-beam-induced-current (EBIC) mode are performed. One of them is a distinction between n− and n+ regions in an EBIC image of SEM with high contrast. The other is a new observation of the defects located at the surface as an EBIC image.