Measurement of Enhanced Gate-Controlled Band-to-Band Tunneling in Highly Strained Silicon-Germanium Diodes

Strained silicon-germanium $(\hbox{Si}_{0.6}\hbox{Ge}_{0.4})$ gated diodes have been fabricated and analyzed. The devices exhibit significantly enhanced gate-controlled tunneling current over that of coprocessed silicon control devices. The current characteristics are insensitive to measurement temperature in the 80 K to 300 K range. Independently extracted valence band offset at the strained $\hbox{Si}_{0.6}\hbox{Ge}_{0.4}/\hbox{Si}$ interface is 0.4 eV, yielding a $\hbox{Si}_{0.6}\hbox{Ge}_{0.4}$ bandgap of 0.7 eV, which is much reduced compared to that of Si. The results are consistent with device operation based on quantum–mechanical band-to-band (BTB) tunneling rather than on thermal generation. Moreover, simulation of the strained $\hbox{Si}_{0.6}\hbox{Ge}_{0.4}$ device using a quantum–mechanical BTB tunneling model is in good agreement with the measurements.