Effect of Uniaxial Tensile Strains at Different Orientations on the Characteristics of AlGaN/GaN High-Electron-Mobility Transistors

The influence of uniaxial tensile strains with different orientations to the conduction channel on the electrical and physical properties of AlGaN/GaN high-electron-mobility transistors (HEMTs) was investigated. The output current decreases with the increase of the tensile strain as the orientation of strain changes from 0° to 90° with respect to the conduction channel. The results of the measured C-V curves show that for the same strain level the two-dimensional electron gas (2DEG) density decreases monotonically to different extents depending on the strain orientation. A conversion of the strain at different orientations to an equivalent strain parallel to the conduction channel shows that the theoretical resultant changes of the 2DEG density are consistent with the experimental results. The corresponding electron mobility is also calculated, which shows a decreasing trend under the tensile strain. Furthermore, using the transient current method, it is established that the detrapping time constant increases as a result of the tensile strain, which is ascribed to the movement of the trap level away from the conduction band.