Epitaxial Si-based tunnel diodes

Tunneling devices in combination with transistors offer a way to extend the performance of existing technologies by increasing circuit speed and decreasing static power dissipation. We have investigated Si-based tunnel diodes grown using molecular beam Ž . q q epitaxy MBE . The basic structure is a p layer formed by B delta doping, an undoped spacer layer, and an n layer formed by Ž . Sb delta doping. In the n-on-p configuration, low temperature epitaxy 300]3708C was used to minimize the effect of dopant segregation and diffusion. In the p-on-n configuration, a combination of growth temperatures from 320 to 5508C was used to exploit the Sb segregation to obtain a low Sb concentration in the B-doped layer. Post-growth rapid thermal anneals for 1 min in the temperature interval between 600 and 8258C were required to optimize the device characteristics. J , the peak current p Ž . density, and the peak-to-valley current ratio PVCR , were measured at room temperature. An n-on-p diode having a spacer layer composed of 4 nm Si Ge , bounded on either side by 1 nm Si, had a J s2.3 kArcm2 and PVCRs2.05. A p-on-n tunnel 0.6 0.4 p Ž . 2 diode with an 8 nm Si spacer 5 nm grown at 3208C, 3 nm grown at 5508C had a J s2.6 kArcm and PVCRs1.7. Q 2000 p Elsevier Science B.V. All rights reserved.