Project Details
Projekt
Func4Punc - Functionalization of AlGaN/GaN HEMTs by additive ferroelectric AlScN for efficient power conversion
Subject Area
Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 563147180
AlGaN/GaN HEMTs are popular in high-speed and high-power electronics due to the intrinsic high breakdown voltage of group-III-nitride materials and the presence of the 2deg at the AlGaN/GaN heterojunctions. To improve performance and broaden their application scope, consistent attempts have been made to combine GaN-based HEMTs with ferroelectric materials. This integration has been aimed at achieving dynamic and non-volatile threshold voltage control for primary memory and adaptable radio frequency / microwave uses. However, while emerging ferroelectrics like AlScN feature ample polarization that enable vast design possibilities to couple charges with the underlying device function, its full utilization has been challenging for scalable device architectures due to the required matching of ferroelectric properties as well as process challenges during the integration of ferroelectric AlScN thin films. These challenges manifest in enhanced leakage current at lower film thicknesses and sensitivity towards topography as well as substrate crystalline orientation, which promotes reduced breakdown voltages below the required coercive field strength for polarization control or formation of the cubic phase and misaligned crystal domains. To address these challenges, this proposal aims to integrate different ferroelectric gate stacks into AlGaN/GaN HEMTs. For this, initially the impact of novel ternary dielectric interlayers with adjustable properties (bandgap, dielectric constant), atomic layer processing steps, floating intermediate metal / semiconductor layers and suitable contact metals on the ferroelectric properties of AlScN thin films is investigated. The most promising material stacks will be integrated in FeHEMTs and their operation characterized to correlate ferroelectric material properties with the resulting transistor properties. Special effort will be spent to investigate interactions between the 2deg charges and polarization charges in operando. Additionally, operation parameter spaces are to be explored and defined to avoid unintended polarization switching during transistor operation. The resulting augmented HEMTs are to be conceptualized for their use in power electronic applications with the prospect of improved energy efficient operation due to the capability of advanced device property calibration. Special attention is being given in this development effort to maintain process compatibility with existing AlGaN/GaN technologies to expand its technology platform with ferroelectric enhanced transistors.
DFG Programme
Priority Programmes
