We present the first experimental demonstration of sub-10-nm diameter GaSb/InAs vertical nanowire (VNW) Esaki diodes. Our devices exhibit excellent current scaling behavior over nearly two decades of diameter. An average Esaki peak current density of 1 MA/cm2 is obtained, among the best when projecting from the state-of-The-Art at our nominal doping level. An average current density of 4 MA/cm2 is demonstrated at mathrm{V}-{ ext{ds}}=0.3 mathrm{V}, which is promising for future ultra-low power VNW tunnel FET applications based on this material system. NEGF quantum transport simulations are carried out. Inelastic tunneling due to phonon emission is found to suppress tunneling current in the positive Vds branch and to widen the Esaki peak in the negative Vds branch, which has long been underestimated.
