Interfacial nanochemistry and electrical properties of Pb(Zr0.3Ti0.7)O3 films on GaN/sapphire

The structure, interfacial nanochemistry, and electrical properties of sol-gel derived Pb(Zr0.3Ti0.7)O3 or PZT (30 / 70) thin films on metal-organic chemical vapor deposited (0001) GaN/sapphire substrates are reported. The X-ray diffraction analysis confirmed a phase-pure and highly oriented (111) PZT and Rutherford backscattering spectroscopy was used to ascertain the Zr/Ti ratio. The secondary ion mass spectrometry depth profile and electron energy loss spectroscopy with high energy and spatial resolution indicated a chemically sharp PZT/GaN interface with insignificant interdiffusion between Pb, Zr, or Ti in PZT and Ga and N in GaN. The lower capacitance density (C / A = 0.35 μF/cm2) and asymmetrical polarization (P ∼ 4 μC/cm2) hysteresis loops of PZT in Pt/PZT/GaN or metal-ferroelectric-semiconductor configuration were attributed to the high depolarization field (Edepol) within PZT. In contrast, PZT in Pt/PZT/Ru/GaN or metal-ferroelectric-metal configuration exhibited high capacitance density (C / A = 1.25 μF/cm2) and polarization (P ∼ 30 μC/cm2).