Abstract
The 8-band k·p parameters which include the direct band coupling between the conduction and the valence bands are derived and used to model optical intersubband transitions in Ge quantum well heterostructure material grown on Si substrates. Whilst for Si rich quantum wells the coupling between the conduction bands and valence bands is not important for accurate modelling, the present work demonstrates that the inclusion of such coupling is essential to accurately determine intersubband transitions between hole states in Ge and Ge-rich Si1−xGex quantum wells. This is due to the direct bandgap being far smaller in energy in Ge compared to Si. Compositional bowing parameters for a range of the key modelling input parameters required for Ge/SiGe heterostructures, including the Kane matrix elements, the effective mass of the Γ2′ conduction band, and the Dresselhaus parameters for both 6- and 8-band k·p modelling, have been determined. These have been used to understand valence band intersubband transitions in a range of Ge quantum well intersubband photodetector devices in the mid-infrared wavelength range.
Highlights
There are many applications in the mid-infrared part of the electromagnetic spectrum which include thermal imaging1 and the unique identification of molecules through absorption spectroscopy.2 For all these applications, sources of mid-infrared light and photodetectors1,3 are key to enable any application
The 8-band kÁp parameters which include the direct band coupling between the conduction and the valence bands are derived and used to model optical intersubband transitions in Ge quantum well heterostructure material grown on Si substrates
Whilst for Si rich quantum wells the coupling between the conduction bands and valence bands is not important for accurate modelling, the present work demonstrates that the inclusion of such coupling is essential to accurately determine intersubband transitions between hole states in Ge and Ge-rich Si1ÀxGex quantum wells
Summary
There are many applications in the mid-infrared part of the electromagnetic spectrum which include thermal imaging and the unique identification of molecules through absorption spectroscopy. For all these applications, sources of mid-infrared light and photodetectors are key to enable any application. There are many applications in the mid-infrared part of the electromagnetic spectrum which include thermal imaging and the unique identification of molecules through absorption spectroscopy.2 For all these applications, sources of mid-infrared light and photodetectors are key to enable any application. Previous work using an 8-band kÁp tool available as Nextnano with scaled 6-band kÁp parameters was sufficient to allow the interband optical absorption for Ge QW quantum confined Stark effect modulators to be determined.. Previous work using an 8-band kÁp tool available as Nextnano with scaled 6-band kÁp parameters was sufficient to allow the interband optical absorption for Ge QW quantum confined Stark effect modulators to be determined.18 This approach, when used provided poor agreement with experimental results for intersubband absorption for Ge-rich heterolayers as it does not accurately account for the direct bandgap coupling between the C-valley and the valence bands.
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