场板抑制GaN高电子迁移率晶体管电流崩塌的机理研究

Study on the suppression mechanism of current collapse with field-plates in GaN high-electron mobility transistors

通过实验和数值器件仿真研究了钝化GaN高电子迁移率晶体管(HEMTs)、栅场板GaNHEMTs和栅源双层场板GaNHEMTs电流崩塌现象的物理机理,建立了电流崩塌强度与帽层中载流子浓度、陷阱电离率和电场的内在联系.研究结果表明,场板可以有效调制帽层中横向和纵向电场的强度分布,并可有效调制纵向电场的方向,减弱栅极附近电场强度,增加场板下方电场强度,这会减弱栅极附近自由电子的横向运动,增强场板下方自由电子的纵向运动,进而可以有效调制帽层中自由电子浓度的分布,提高陷阱的电离率,减小器件的电流崩塌.

The physical mechanisms underlying current collapse effects in the passivated GaN high-electron mobility transistors （ HEMTs）,the gate field-plated GaN HEMTs and the gate-source field-plated GaN HEMTs are investigated in experiments and numerical device simulations. And the intrinsic relationships of the current collapse with the carrier concentration,the probability of traps ionization,and the electric field within the cap layer are established. Results show that the direction of the longitudinal electric field,as well as the intensity distribution of both the transverse and longitudinal electric fields within the cap layer,can be modulated effectively by the field-plates. The electric field intensity near the gate is reduced and that beneath the field-plates increased. Due to the effects of the field-plates on electric field,the transverse movement of electrons near the gate is reduced,and the longitudinal electron movement beneath the field-plates is increased. These affects the electron concentration distribution and the ionization probability of the traps in the cap layer,which makes field-plates effective for the reduction in the current collapse.