Abstract
Critical thicknesses of two-dimensional to three-dimensional growth in GexSi1−x layers were measured as a function of composition for different growth temperatures. In addition to the (2 × 1) superstructure for a Ge film grown on Si(100), the GexSi1−x layers are characterized by the formation of (2 × n) reconstruction. We measured n for all layers of Ge/GexSi1−x/Ge heterosystem using our software with respect to the video recording of reflection high-energy electron diffraction (RHEED) pattern during growth. The n reaches a minimum value of about 8 for clear Ge layer, whereas for GexSi1−x films, n is increased from 8 to 14. The presence of a thin strained film of the GexSi1−x caused not only the changes in critical thicknesses of the transitions, but also affected the properties of the germanium nanocluster array for the top Ge layer. Based on the RHEED data, the hut-like island form, which has not been previously observed by us between the hut and dome islands, has been detected. Data on the growth of Ge/GexSi1−x/Ge heterostructures with the uniform array of islands in the second layer of the Ge film have been received.
Highlights
The Ge/GexSi1−x/Ge heterosystems with alternating layers of quantum dots and quantum wells are of great practical interest for the fabrication of mid-infrared photodetectors based on intraband transitions [1]
Identifying the moments of 2D to 3D transitions at various thicknesses of the GexSi1−x layer allowed the 2D to 3D transition thickness of the Ge film to be determined as a function of the GexSi1−x thickness for different Ge content in GexSi1−x layers and growth temperature
The surface morphology of the germanium island film on the surface of GexSi1−x solid solution changes essentially if germanium islands are formed as hut clusters before growing the GexSi1−x layer
Summary
The Ge/GexSi1−x/Ge heterosystems with alternating layers of quantum dots and quantum wells are of great practical interest for the fabrication of mid-infrared photodetectors based on intraband transitions [1]. The authors of a study [16] assume that the increased island density is caused by an increased surface roughness after the SiGe deposition, while the islands increased in size due to increasing Si content that resulted from mixing at high growth temperature and from a decrease of the wetting layer in thickness. The latter is accounted for by the accumulation of elastic strain energy in the SiGe layer. This result was obtained due to a higher quantum dot density which provides more effective capturing of charge carriers
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