Abstract
The experimental THz-excitation spectroscopy technique for determining heterojunction band offsets is suggested. When photoexcited electrons gain sufficient energy to pass the potential barrier corresponding to a conduction band offset, an amplitude of THz-emission pulse sharply increases, which allows for direct measurements of the offset value. The technique is applied for determining GaAsBi-GaAs band offsets. The deduced conduction band offset of GaAsBi-GaAs heterojunction has about 45% of an energy gap difference at the Bi concentrations x < 0.12 investigated.
Highlights
Terahertz radiation (THz) emission from semiconductor surfaces was demonstrated by Auston group[1]
Since the surface THz emission is a universal phenomenon in semiconductors, THz time domain spectroscopy can be used as a characterization tool of these materials
Two main mechanisms of THz emission from femtosecond laser excited semiconductor surfaces are the photocurrent surge in the surface electric field and the spatial separation of more mobile photoexcited electrons and less mobile holes at the surface
Summary
Terahertz radiation (THz) emission from semiconductor surfaces was demonstrated by Auston group[1]. Since the surface THz emission is a universal phenomenon in semiconductors, THz time domain spectroscopy can be used as a characterization tool of these materials. Two main mechanisms of THz emission from femtosecond laser excited semiconductor surfaces are the photocurrent surge in the surface electric field and the spatial separation of more mobile photoexcited electrons and less mobile holes at the surface (the photo-Dember effect).
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