The intersubband absorption in self-assembled boron-doped multiple Ge quantum dots is observed. The structures used consist of 20 periods of boron-doped Ge dot layers and undoped Si barriers. The infrared absorption as a function of wavelength is measured by Fourier transform infrared spectroscopy using a waveguide geometry. Absorption peaks in the mid-infrared range have been observed, which are attributed to the transitions between the first two heavy hole states of the Ge quantum dots. The polarization dependence measurement is used to study the nature of the transitions. This observation suggests the possible use of multiple Ge quantum dots for infrared detector application.

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