Fig. 2: Polarization characteristics of WZ ferroelectric ScAlN/GaN heterostructure.
From: Experimental determination of giant polarization in wurtzite III-nitride semiconductors
a HAADF-STEM image of the as-grown ScAlN/GaN heterostructure, exhibiting an atomically sharp interface. b Typical P-E hysteresis loop recorded from a ScAlN capacitor at 1 kHz without subtracting electric leakage. The inset shows a schematic of the ScAlN metal-ferroelectric-semiconductor (MFS) capacitor structure. c, d ABF-STEM images of ScAlN, captured from (c) positively and (d) negatively biased MFS capacitors, as indicated in (b). The superimposed metal (pink) and nitrogen (blue) atoms highlight the atomic stacking sequence, revealing N- and M-polar lattices in (c) and (d), respectively. e Monopolar measurements executed on ScAlN MFS capacitors with opposite initial polarization states: (i, ii) fresh M-polar ScAlN, exhibiting upward spontaneous polarization, and (iii, iv) switched N-polar ScAlN, presenting downward spontaneous polarization. The insets depict the applied voltage pulses and the evolution of polarization orientation under an external electric field, with arrows in the ScAlN/GaN heterostructures indicating the polarization orientation.
