New ferroelectric coating method unlocks stable power chips for electric vehicles
Researchers have engineered a multilayer ferroelectric gate coating that enables gallium nitride power semiconductors to operate reliably in enhancement mode—a requirement for next-generation power management in EVs and industrial equipment. The technique, involving careful control of annealing sequences, achieves threshold voltages above 5 volts with enhanced stability, addressing a persistent manufacturing bottleneck in high-efficiency power electronics.
Originaltitel: Study of Ferroelectric Stack Thickness and Annealing Sequence Effects on GaN HEMTs with Hybrid Ferroelectric Stacks Gate
<p>Achieving a stable enhancement-mode (E-mode) operation with a sufficiently high threshold voltage (V th) remains a key challenge for GaN power HEMTs. This work investigates the effects of ferroelectric stack thickness and annealing sequence on GaN MOS-HEMTs grown on SiC substrate incorporating a hybrid ferroelectric gate stack composed of Al2O3/HZO/Al2O3 with an embedded HfON charge-trap layer between HZO and Al2O3 layers. Devices with different HZO stack thicknesses were subjected to postdeposition annealing (PDA) or postmetallization annealing (PMA) at 400 degrees C in N2 ambient. PMA-treated devices exhibit a higher and more stable V th, significantly reduced C-V dispersion, and improved robustness after gate-bias initialization compared with PDA-treated devices. The optimized PMA device with a thicker ferroelectric stack achieves a positive V th of up to 5.39 V, enabling a programmable E-mode operation. In addition, ferroelectric metal-ferroelectric-metal capacitors demonstrate pronounced hysteresis behavior in PMA-treated samples, with a remanent polarization (2Pr) of 36.63 mu C/cm2. These results demonstrate that annealing-sequence-controlled hybrid ferroelectric gate engineering is an effective strategy for realizing high-V th, stable enhancement-mode GaN HEMTs.</p>