Physics

Biography

Biography: Zhaojun lin

Abstract

Due to inverse piezoelectric effect and device processing, the uneven strain distribution of the barrier layer for GaN-based heterostructure field-effect transistors (GaN-based HFETs.)is unavoidable. A new scattering mechanism, the polarization Coulomb field scattering which is related to the uneven strain distribution of the barrier layer, is proposed. This talk introduces the theoretical model of the polarization Coulomb field scattering and the relationship between the polarization Coulomb field scattering and the device structures of GaN-based HFETs. Moreover, the influence of the polarization Coulomb field scattering on the characteristics of GaN-based HFETs are also discussed. Such as, the effect of the polarization Coulomb field scattering on parasitic source access resistance and extrinsic transconductance in AlGaN/GaN HFETs, it is found that the variation of the parasitic source access resistance originates from the polarization Coulomb field scattering, and the effect of the polarization Coulomb field scattering on the parasitic source access resistance is more significant for the device with a longer gate length or a shorter gate-source distance. The behaviors of the measured transconductance for the fabricated AlGaN/GaN HFETs confirm the effect of polarization Coulomb field scattering. In addition, the effects of the polarization Coulomb field scattering on device linearity in AlGaN/GaN HFETs is also found. The single-tone power of the AlGaN/GaN HFETs with different gate widths was measured. A distinct improvement in device linearity was observed in the sample with a larger gate width. The analysis of the variation of the parasitic source access resistance showed that, as the gate bias is increased, the polarization Coulomb field scattering can offset the increased polar optical phonon scattering and improve the device linearity.