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

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Strained silicon-germanium <formula formulatype="inline"><tex>$(\hbox{Si}_{0.6}\hbox{Ge}_{0.4})$</tex> </formula> 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 <formula formulatype="inline"><tex>$\hbox{Si}_{0.6}\hbox{Ge}_{0.4}/\hbox{Si}$</tex> </formula> interface is 0.4 eV, yielding a <formula formulatype="inline"> <tex>$\hbox{Si}_{0.6}\hbox{Ge}_{0.4}$</tex></formula> 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 <formula formulatype="inline"><tex>$\hbox{Si}_{0.6}\hbox{Ge}_{0.4}$</tex></formula> device using a quantum–mechanical BTB tunneling model is in good agreement with the measurements. </para>