Photoinduced Absorption Spectrum of GeSi/Si Quantum Dots in the Mid-IR and Terahertz Ranges under Resonant and Non-resonant Optical Pumping

Vacuum Fourier spectrometer was used to obtain mid-infrared photoinduced absorption spectra of undoped GeSi/Si quantum dots at liquid helium temperature under different conditions of interband optical pumping. High-intensity peaks in the absorption spectra are associated with intraband hole transitions from the ground and excited states of the quantum dot to the continuous spectrum. The less intense long-wavelength peak corresponds to the hole transitions between the ground and excited states. In the terahertz spectral range, equilibrium absorption spectra were obtained, associated with transitions from the ground to a nearby excited state of holes. Structures with GeSi/Si quantum dots can be used to develop detectors of mid-infrared radiation.