Electron transport properties of strained channel AlGaN/GaN HEMT based on an improved strain mobility model

In order to further improve the current characteristics of AlGaN/GaN HEMTs, a strained GaN channel AlGaN/5-nm-GaN/InGaN HEMT(SGC-HEMT) device structure with an InGaN relaxation layer inserted into the channel of non-under-gate was proposed. The electron transport properties of SGC-HEMT device were investigated by Sentaurus TCAD simulation. Based on the modified strain mobility model, the magnitude of the channel strain was adjusted by changing the Indium composition of the InGaN relaxation layer, while taking into account the 5-nm-GaN channel strain and the additional strain of the AlGaN barrier layer. The theoretical relationship between polarization induced electron gas distribution and channel strain was discussed. The simulation results show that the introduction of strain significantly increases the drain saturation current of the device, when the Indium composition is 0.02, the tensile strain of the strained GaN(GaNs) channel layer and AlGaN barrier layer is 0.225%, and the drain saturation current of the SGC-HEMT is 0.914 A·mm⁻¹, compared with the conventional AlGaN/GaN HEMT's 0.701 A·mm⁻¹, an improvement of 30.63%. With the further application of channel tensile strain, the scattering mechanism is strengthened, the growth of drain saturation current and effective mobility is flattened, and the gate leakage is gradually deteriorated. In addition, since no strain is applied to the channel below the gate, the threshold voltage basically does not change with the strain. Finally, the effective mobility under different tensile strains was extracted. It can be seen that as the tensile strain of the channel increases, the effective mobility in the low electric field region is higher, while the decay in the high electric field region is slower. The research results on the electron transport properties of strained channel GaN HEMTs are beneficial to further improve the electrical properties of AlGaN/GaN HEMTs.