Showing papers by "Eugene A. Fitzgerald published in 1996"
TL;DR: In this article, a cross-sectional transmission electron microscopy, spreading resistance, and electron beam induced current (EBIC) studies eliminate the dislocations themselves as a possible source of this type conversion, by demonstrating that the spatially invariant hole concentration of 2×1014 cm−3 is not correlated to the dislocation density, which decreases from ∼108 cm−2 in the graded region to 7×105 cm− 2 in the 30% Ge cap.
Abstract: Strain‐relaxed, compositionally graded Ge0.3Si0.7/Si heterostructures grown by ultrahigh vacuum chemical vapor deposition at 650 °C are shown to display a consistent change from p‐type to n‐type conductivity as a function of rapid thermal annealing (RTA) temperature in the range 700–850 °C. Cross‐sectional transmission electron microscopy, spreading resistance, and electron beam induced current (EBIC) studies eliminate the dislocations themselves as a possible source of this type conversion, by demonstrating that the spatially invariant hole concentration of 2×1014 cm−3 is not correlated to the dislocation density, which decreases from ∼108 cm−2 in the graded region to 7×105 cm−2 in the 30% Ge cap. To identify the source of type conversion, a systematic investigation was performed on 650 °C as‐grown and annealed samples with deep‐level transient spectroscopy (DLTS), photoluminescence (PL) and capacitance–temperature (C–T) measurements. DLTS measurements on as‐grown samples reveal a complex spectrum of dee...
29 citations
TL;DR: In this article, the electrical activity of threading dislocation defects in relaxed GeSi films with a novel, high-resolution optical technique was studied. But the authors only used a near-field scanning optical microscope to measure spatially resolved photoresponse while simultaneously imaging the surface topography.
Abstract: We study the electrical activity of threading dislocation defects in relaxed GeSi films with a novel, high‐resolution optical technique. A near‐field scanning optical microscope is used to measure spatially resolved photoresponse while simultaneously imaging the surface topography. We have convincingly established that shallow topographic depressions in these films are electrically active threading dislocations. The apparent sizes of the dislocations in the photovoltage images are in agreement with estimates based on the junction geometry and the near‐field optical excitation spot size. We can clearly observe photoresponse changes at ≤100 nm lateral scale, a tenfold improvement from far‐field optical techniques. This higher resolution is due to reduction of the excitation volume and of the carrier lifetime near defects.
17 citations