Lattice compression of Si crystals and crystallographic position of As impurities measured with x-ray standing wave spectroscopy

Abstract

In an earlier letter [Appl. Phys. Lett. 68, 3090 (1996)] we reported results about heavily arsenic doped silicon crystals, where we unambiguously showed, based on x-ray standing wave spectroscopy (XSW) and other techniques, that electrically deactivated As remains essentially substitutional. In this article we present the analysis methodology that led us to said conclusion, and show how from further analysis it is possible to extract the compression or expansion of thin epitaxial layers. We report the evolution of the compression of highly As doped Si epitaxial layers as deactivation takes place. The XSW measurements required a very small thickness of the doped layer and a perfect registry between the substrate and the surface layer. We found larger values for compression than previously reported, which may be explained by the absence of structural defects on our samples that relax the interface stress. Our results show a saturation on the compression as the electron concentration increases. We also report an estimation of the small displacement from perfect substitutional positions suffered by deactivated As.

Correlation of local structure and electrical activation in arsenic ultrashallow junctions in silicon

“…1 However, active As distribution in Si at concentrations higher than 10 20 cm −3 has a tendency to electrically deactivate when subjected to thermal treatment in the 300-750°C range, [2][3][4] even without forming extended precipitates. This was confirmed by Rutherford backscattering spectroscopy 5,6 ͓which revealed just slight atom displacement ͑0.2 Å͔͒, 7 x-ray standing wave spectroscopy, 8,9 and transmission electron microscopy. 10,11 Several experimental results suggested the clustering around a vacancy of a number of As atoms up to 4 ͑As n V with n Յ 4͒ 12 as the main mechanism responsible for the deactivation.…”

Evidence for a New Class of Defects in Highlyn-Doped Si: Donor-Pair-Vacancy-Interstitial Complexes

“…The r cutoff can be changed by tuning the inner angle of the LA detector, but (see below) 0:3 A is useful for Sb. Note that while the average r of impurities in a crystal can be measured using x-ray standing waves [13] or Rutherford backscattering and ion channeling [14], our STEM-based approach has the ability to measure r one impurity atom at a time. This is particularly important for studying defects because we can focus on the r of only those impurities whose lattice positions are consistent with a pair defect.…”

Stress Effects on As Activation in Si

“…A detailed explanation can be found in Ref. In spite of longer As-Si bond as compared to the Si-Si bond length, there have been many experiments observing lattice contractions in heavily As-doped Si, which have been attributed to electrons in the conduction band [6,11,12]. To extract the energy vs. strain curve, we calculated the total free energy of 64 atom (or 63 atom with vacancy) supercells using the DFT code VASP [8] in generalized gradient approximation (GGA) with PW91 potential [9].…”