ECS Transactions · 2010 · 18 citations · 0 references
EngineeringElectrical EngineeringMaterials ScienceMicroelectronicsSemiconductor DevicesSemiconductor MaterialsField-effect TransistorsIntegrated Circuit DesignMetal-oxide-semiconductor Field-effect TransistorsSemiconductor Device MaterialsSemiconductor HeterostructuresTunnelingBand GapDirect Band GapHeterojunction DevicesHeterostructure Field-effect TransistorsHeterostructure TransistorsIndirect Band GapTunneling CurrentTunneling Field-effect Transistors
Tunneling field‑effect transistors promise sub‑60‑mV/decade subthreshold slopes that could overcome CMOS power/performance limits, but silicon’s large indirect band gap hampers band‑to‑band tunneling, making Si‑based TFETs challenging despite silicon’s VLSI heritage. This study investigates whether Si/SiGe heterojunction tunneling transistors can achieve practical performance by experimentally varying the heterojunction band offset and analyzing the suitability of Si‑based materials versus direct‑gap systems for TFETs. Experimental results show that increasing the heterojunction band offset in Si/SiGe HETTs enhances device performance, indicating that Si‑based TFETs can be viable but may still require direct‑gap materials for optimal performance.
Tunneling field effect transistors (TFETs) are a device technology that has the potential to achieve sub-60-mV/decade subthreshold slope and therefore could potentially overcome the power / performance bottleneck facing the CMOS industry today. It would be highly desirable to fabricate such devices using Si-based materials due to the proven capability of Si for VLSI circuits. However the large, indirect band gap of Si is not conducive to achieving large band-to-band tunneling currents. This paper presents experimental results on Si/SiGe heterojunction tunneling transistors (HETTs), where it is demonstrated that increasing the heterojunction band offset leads to enhanced device performance. An analysis is also provided addressing whether or not Si-based materials are suitable for TFETs or if material systems with direct band gaps and that allow more aggressive heterostructure engineering will be required to achieve the performance levels necessary for practical applications.