Carrier density dependent energy band-gap and phonon frequency in Ge

Conference Dates

May 21-25, 2017


Dopant atoms in nano-devices should be countable and dopant atom discreteness cannot be ignored. The energy band- gap and phonon frequency in a semiconductor are, however, believed to be material-specific constants except quantum size effects, though apparent band-gap narrowing and phonon-softening in doped semiconductors have been experimentally reported and theoretically discussed [1, 2]. On the other hand, in doped semiconductors, it is experimentally difficult to differentiate dopant effects from free carrier ones. Thus, the objective of this study is to separate the dopant from free carrier effects on “intrinsic properties in Ge” experimentally, and to discuss about their physical implications. Lightly doped GeOI wafers were used. Bottom gated FETs were fabricated with Y2O3 passivation on the top surface [3], as shown in Fig. 1. Thanks to this sample structure, PL and Raman investigations were successfully carried out for a same sample as a function of the bottom gate bias, from the top surface without being masked by the top gate metal.

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