Multimode GaN Transistors with Ultrawide Threshold Voltage Control Enabled by Passivation-Induced Stress–Strain–Polarization Coupling

Multimode GaN transistors achieve multimodality by exploiting a broadly tunable and ultrawide threshold voltage ( V TH ) that covers both depletion-mode (D-mode) and enhancement-mode (E-mode) operation. This V TH tunability is enabled by epitaxial growth of ultrathin AlN barriers with high interface quality and strong electrostatic control, combined with tensile stress introduced by PECVD-SiN passivation. Through stress–strain–polarization coupling (SSPC), strain along [0001] approaching −4.2% was generated, which increased the 2DEG density by more than 1 order of magnitude and thus enabled an ultrawide V TH window. The evolution among background-carrier, MOS-like, and D/E-mode high-electron mobility transistor (HEMT) conduction modes under different passivation thickness ( P T ) was further clarified by simulations, accounting for the observed multimode behavior. SSPC was thus supported as a compact and low-damage method for etch-free tuning of polarization, carrier density, and V TH . The continuously tunable conduction modes provide multimode GaN transistors multiple functionalities, enabling applications in RF amplification, multimode neuromorphic computing, efficient power conversion, and complex circuit optimization.