Effects of Damage-Impurity Interaction on Electrical Properties of Se + -Implanted GaAs
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EFFECTS OF DAMAGE-IMPURITY INTERACTION ON ELECTRICAL PROPERTIES OF Se+-IMPLANTED GaAs
D. K. SADANA, J. WASHBURN, M. D. STRATHMAN Lawrence Berkeley Laboratory, University of California, Berkeley, G. R. BOOKER Department of Metallurgy, University of Oxford,
CA 94720
Oxford, England
M. H. BADAWI Department of Electronics and Electrical Engineering, Guildford, Surrey, England
University of Surrey,
ABSTRACT Interaction of impurities with the "visible defects" in hot implanted Cr doped semi-insulating (100) GaAs has been investigated. The defects studies were performed using transmission electron microscopy (TEM) and MeV He+ channeled Rutherford backscattering. The defects distribution was obtained by 90* cross-sectional TEM (XTEM). The atomic concentration profiles of Se, and carrier-concentration and mobility profiles were obtained by secondary ion mass spectrometry (SIMS) and Hall measurements in conjunction with chemical stopping, respectively. Comparison of defects, atomic and electrical profiles, showed the formation of secondary defects at and beyond the projected range (Rp), a significant amount of Se+ diffusion beyond , and compensation of electrical carriers caused mainly by the point defects present
in hot implanted GaAs.
INTRODUCTION The effect on electrical properties of the ion implantation induced damage which is left after subsequent furnace annealing in Si and GaAs has been investigated earlier [1-3]. The depth profiles of visible defects as obtained by cross-sectional transmission electron microscopy (XTEM) and electrical profiles obtained by Hall measurements in conjunction with layer stripping has demonstrated that both in Si and GaAs, there are strong correlations between the structural and electrical properties of these materials. In Si, a significant number of impurity atoms were found to segregate near the visible defects (defects visible by TEM) causing a pronounced distortion in the distribution of the implanted impurity. This distortion was also reflected in the electrical profiles. Similar correlations for ion-implanted GaAs are not available at present [3]. The aim of this work was therefore to understand the structural-electrical properties correlation in Se+-implanted GaAs. For this purpose, cross-sectional electron microscopy, MeV He+ channeling, secondary ion mass spectrometry (SIMS), and electrical measurements were performed on the same sample. It has been observed that the effect of the visible defects on the distribution of the implanted impurity (Se) is not straightforward. It has been deduced from the findings that the point defects and their complexes play the dominant role in determining the electrical properties of Se+-implanted GaAs.
516 EXPERIMENTAL Semi-insulating Cr-doped (100) GaAs were implanted in a non-channeling 2 4 direction14 with2 Se+ ions at 450 KeV to doses of 1.0 x 101 /cm and 5.0 x 10 /cm . The substrate temperature was kept at 200%C during the The resulting specimens were encapsulated with a 5000 A thick implantation. Al layer and annealed at
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