Spectral heat phonon blocking characteristics across inter-mixed and oxidized semiconductor interfaces

In this work, we spectrally investigate thermal transport characteristics across the interfaces formed between Al metal and various semiconductors, such as Si, Ge, and GaAs by exploiting an acoustic phonon transmission spectroscopy technique which provides full transmission spectra of three acoustic branches. We control the interface conditions by adjusting an air exposure time after the HF treatment, and observe that the phonon transmission becomes significantly reduced from the high frequency side. Considering that the wavelength of heat phonons ranges from about 0.5 nm to 10 nm, we discuss the variations of the phonon transmittance spectra based on electronic and phononic states as well as the interface morphology.