Research On Junctionless Field Effect Transistors Based On Negative Capacitance Technology

With the rapid development of semiconductor technology,the size of traditional transistor devices has been continuously scaled down to the physical limit.The actual development speed has fallen behind the predicted speed of Moore's Law,which has brought great challenges for further development of semiconductor technology,such as short-channel effects(SCE)and power consumption caused by size reduction.In order to solve these problems,various new materials and new structures have been developed continuously.Among these,junctionless field effect transistors(JLFETs)and negative capacitance field effect transistors(NCFETs)have been considered as the promising candidates.In our work,based on the experimental results of the JLFET,we successfully demonstrated a hybrid channel NC-JLFET incorporating the NC effect of the HfAlO ferroelectric material by simulation,which effectively reduced the power consumption.Our work can be divided into the following three parts.Firstly,an HfAlO ferroelectric capacitor with good ferroelectric property and JLFETs with two different channels of pnpn and pop multilayers were achieved by experiments.The electrical characteristics of the JLFETs including on/off-state current ratio(ION/IOFF),threshold voltage,subthreshold swing(SS)were investigated.The results showed that the JLFET with the pnpn multilayer channel exhibited better performances as compared to the JLFET with the pop multilayer channel,which could be attributed to the depletion effect in the vertical direction of the channel,resulting in the better gate controlability.Secondly,the simulation of the JLFETs was carried out by TCAD.Based on the experimental parameters of the device materials and structures,the device characteristics including electric field distribution and electric field density were simulated for the JLFETs with two different channels of pnpn and pop multilayers,which also explained the superiority of the pnpn multilayer channel.Finally,a NC-JLFET combining the NC effect of the ferroelectric material was designed and simulated by TCAD.Based on the relative existing theoretical NC models,the effect of capacitance matching on the NC devices was investigated.An NC-JLFET by connecting a JLFET in series with an HfAlO ferroelectric capacitor was demonstrated by simulation with a very high ION/IOFF of 108 and extremely low SS of 34 mV/decade,which was lower than the fundamental limit of the classical transistor.In this work,based on the experimental results of the JLFET and HfAlO ferroelectric capacitor,the NC-JLFET simulation was carried out by TCAD.Excellent performances were achieved by combining the advantages of the JLFET and NCFET.The present results show that the designed NC-JLFET has the high potential in future application of continuously scaled-down low-power devices and circuits.