Overgrown Si/SiGe resonant interband tunnel diodes for integration with CMOS

The incorporation of tunnel diodes with field effect transistors (FET) can improve the speed and power capability in electronic circuitry. This has been realized in III-V materials by demonstrating a low power refresh-free tunneling-SRAM and high performance compact A/D converter. A new thrust to integrate tunnel diodes with the mainstream CMOS technology led to the invention of Si/SiGe resonant interband tunnel diode (RITD) (S.L. Rommel et al., Appl. Phys. Lett., vol. 73, pp. 2191-93, 1998) with the highest reported peak-to-valley current ratio (PVCR) of 6.0 (K. Eberl, J. Crystal Growth, 227-228, pp. 770-76, 2001). The structure consists of a SiGe spacer i-layer sandwiched between two delta-doped planes grown by low-thermal molecular beam epitaxy (LT-MBE) (N. Jin et al., IEEE Trans. Elec. Dev., vol. 50, pp. 1876-1884, 2003). By adjusting the spacer layer thickness, the peak current density (Jp) can be adjusted from 0.1 A/cm² up to 151 kA/cm² (N. Jin et al., App. Phys. Lett., 83, pp. 3308-3310, 2003). Recently, monolithic integration of RITD with CMOS has been realized, demonstrating a low-voltage operation of a monostable-bistable logic element (MOBILE) (S.Sudirgo et al., Proc. 2003 Int. Semic. Dev. Res. Symp., pp. 22, 2003). In this study, RITD layers were grown through openings in a 300 nm thick chemical vapor deposition (CVD) SiO₂ layer.