E-mode AlGaN/GaN HEMT with ScAlN/ScN charge trap-coupled ferroelectric gate stacks

A fully epitaxial ferroelectric ScAlN/AlGaN/GaN HEMT coupled with an ultrathin ScN charge trap layer for enhancement-mode operation is demonstrated. The ultrathin ScN acts as an electron reservoir to trap and store the electrons from the 2-dimensional electron gas channel region, transitioning the operation of the GaN high electron mobility transistor from the depletion-mode to the enhancement-mode, while the fully epitaxial nature enables low interface defect density and steep slope operation. The initialization process by applying a positive gate bias to inject carriers to the ScN layer is observed to shift the threshold voltage (Vth) from −1.2 to +1.3 V. The fabricated device also shows a steep subthreshold swing as low as 61 mV/dec and exhibits good stability, providing a promising pathway for power-efficient and multifunctional applications.