Electrical performance estimation and comparative study of heterojunction strained and conventional gate all around nanosheet field effect transistors

Reza Abbasnezhad – Hassan Rasooli Saghai – Reza Hosseini – Aliasghar Sedghi – Ali Vahedi

   In this paper, we propose a novel type of Gate All Around Nanosheet Field Effect Transistor (GAA NS FET) that incorporates source heterojunctions and strained channels and substrate. We compare its electrical characteristics with those of the Heterojunction Gate All Around Nanosheet Field Effect Transistor (Heterojunction GAA NS FET) and the Conventional Gate All Around Nanosheet Field Effect Transistor (Conventional GAA NS FET). We investigate the impact of electrostatic control on both DC and analog parameters such as gate capacitance (C_gg), transconductance (g_m) , and cut-off frequency (f_T) for all three device types. In our Proposed GAA NS FET, we employ Germanium for the source and substrate regions, Silicon/Germanium/Silicon (Si/Ge/Si) for the channel, and Silicon for the drain region. The introduction of strain into the nanosheet and the use of a heterojunction structure significantly enhance device performance. Before utilizing a model to analyze a semiconductor device, it is crucial to accurately determine and elaborate on the model parameters. In this case, we solve the Density Gradient (DG) equation self-consistently to obtain the electrostatic potential for a given electron Fermi-level distribution, use the Shockley-Read-Hall (SRH) equation to estimate carrier generation, account for bandgap narrowing in transport behavior, and consider auger recombination. Our general results indicate a notable improvement in drain current, transconductance, and unity-gain frequency by approximately 42%, 53%, and 31%, respectively. This enhancement results in superior RF performance for the Proposed GAA NS FET compared to both the heterojunction GAA NS FET and the conventional GAA NS FET.

Keywords: nanosheet, heterojunction GAA NS FET, conventional GAA NS FET, density gradient, on-state, off-state

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