Observation of polarization pinning effect in PZT/AlGaN/GaN heterostructure

PZT/AlGaN/GaN metal-ferroelectric-semiconductor (MFS) heterostructure is fabricated and characterized by C-V measurement. A distinct asymmetric shift of C-V curve is observed that when the up-sweep (from negative to positive) starting voltage increases from -10 V to -18 V, the C-V curve shifts positively with the threshold voltage varying from -2.4 V to 1.1 V, whereas the down-sweep (from positive to negative) C-V curve hardly move with different starting voltage. The field-history dependent polarization effect of ferroelectrics is involved into a self-consistent calculation, by which the nature of the asymmetric C-V curve shift is disclosed to be the polarization pinning effect of the underlying AlGaN layer. The results take an insight into the interface polarization coupling in GaN-based MFS structure for memory device applications.