Abstract
Strain is one of the important factors affecting the two-dimensional electron gas (2DEG) transform in AlGaN/GaN material based high electron mobility transistors (HEMTs) by polarization effects. In this paper, the effects of inhomogeneous biaxial strain in different regions of the AlGaN barrier layer on electrical properties of normally-off HEMTs with p-GaN gate were discussed. The results show that biaxial strain applied in three regions has different influence on transfer, output and breakdown characteristics of the device. The strain applied in region under gate has the most significant impact on threshold voltage and drain saturation current with a decreasing of 39% and an increasing of 97% respectively as the strained lattice constant increases from 3.173061Å to 3.187229Å.While, strain applied between gate and drain electrode can improve the off-state breakdown voltage by 12% with the increasing of strained lattice constant.
Highlights
High Electron Mobility Transistors (HEMTs) based on AlGaN/GaN heterostructures became attractive candidates for high switching frequency, high breakdown voltage and high power due to their excellent electrical properties, compared to their silicon (Si) counterparts [13]
Most AlGaN/GaN HEMTs exhibit normally-on operation since 2DEG is intrinsically existed in the AlGaN/GaN interface when the HEMT is operating at a gate bias of less than zero volts [4,5]
Simin G. et al [10] revealed that gate bias-induced inhomogeneous strain in the AlGaN barrier will cause a decrease in polarization charge and reduction in 2DEG in normally-on HEMT device by experiments
Summary
High Electron Mobility Transistors (HEMTs) based on AlGaN/GaN heterostructures became attractive candidates for high switching frequency, high breakdown voltage and high power due to their excellent electrical properties, compared to their silicon (Si) counterparts [13]. Simin G. et al [10] revealed that gate bias-induced inhomogeneous strain in the AlGaN barrier will cause a decrease in polarization charge and reduction in 2DEG in normally-on HEMT device by experiments. Ahmeda K. et al [11] found that applying strain in drain region will cause changes in the total polarization, affecting 2DEG density in the channel. As far as we known, there are few reports on the strain effect in the AlGaN barrier of normally-off HEMT with a p-GaN gate. Numerical simulations of the effects of inhomogeneous biaxial strain in AlGaN barrier layer on the electrical properties in a normally-off HEMTs with pGaN gate are discussed. When the strained lattice constant (a) in AlGaN barrier layer changes, the external biaxial strain will change correspondingly. 0.06% according to the stain model [9] on which the investigations are based
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