Subthreshold Electron Transport Properties of Ultrascaled Phase Change Memory

This letter investigates the subthreshold electron transport properties of ultrascaled phase change material (PCM) GeTe, which is sandwiched by TiN electrodes, by using
$ab~initio$
molecular dynamics, density functional theory, and Green's function. Our purely
$ab~initio$
simulations reproduce the measured current–voltage curve characteristics of crystalline
$(c\hbox{-})$
and amorphous
$(a\hbox{-})$
PCM. The on/off ratio and the underlying electron transport mechanism are explained. The electron transport properties of ultrascaled
$c$
-PCM are dominated by metal-induced gap states, and the measured linear and exponential shapes of the subthreshold current–voltage curve of ultrascaled
$a$
-PCM are a consequence of both the bias window enlarging and the bias-induced change of transmission.