Anomalous change of carrier transport property of ferroelectric Hf0.5Zr0.5O2 thin films in the first poling treatment

Carrier transport properties of ferroelectric Hf0.5Zr0.5O2 (HZO) thin films have been investigated on metal-ferroelectric-metal (MFM) capacitor in the first current flow of ferroelectric poling treatment. In current–voltage (I–V) measurement of MFM capacitor, a kink or discontinuity point of derivative in I–V characteristic appears, and after the cyclic voltage sweep this kink disappears. This phenomenon is different from the ferroelectric instabilities after several thousand or million voltage cycle applies reported as the wake-up and fatigue. From the analysis using Poole-Frenkel plot of I–V characteristics, it is suggested that irreversible trap generation by electric field apply occurs in poling treatment.

Strong electron–phonon coupling influences carrier transport and thermoelectric performances in group-IV/V elemental monolayers

The interactions between electrons and phonons play the key role in determining the carrier transport properties in semiconductors. In this work, comprehensive investigations on full electron–phonon (el–ph) couplings and their influences on carrier mobility and thermoelectric (TE) performances of 2D group IV and V elemental monolayers are performed, and we also analyze the selection rules on el–ph couplings using group theory. For shallow n/p-dopings in Si, Ge, and Sn, ZA/TA/LO phonon modes dominate the intervalley scatterings. Similarly strong intervalley scatterings via ZA/TO phonon modes can be identified for CBM electrons in P, As, and Sb, and for VBM holes, ZA/TA phonon modes dominate intervalley scatterings in P while LA phonons dominate intravalley scatterings in As and Sb. By considering full el–ph couplings, the TE performance for these two series of monolayers are predicted, which seriously downgrades the thermoelectric figures of merits compared with those predicted by the constant relaxation time approximation.