Measurement of enhanced gate-controlled band-to-band tunneling in highly strained silicon-germanium diodes

Strained silicon-germanium (Si0.6Ge0.4) 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 Si0.6Ge0.4/Si interface is 0.4 eV, yielding a Si0.6Ge0.4 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 hand-to-hand (BTB) tunneling rather than on thermal generation. Moreover, simulation of the strained Si0.6Ge0.4 device using a quantum-mechanical BTB tunneling model is in good agreement with the measurements.