Resonant interband tunneling diodes on silicon substrates are demonstrated using a Si/Si 0.5 Ge 0.5 /Si heterostructure grown by low temperature molecular beam epitaxy which utilized both a central intrinsic spacer and ␦-doped injectors. A low substrate temperature of 370°C was used during growth to ensure a high level of dopant incorporation. A B ␦-doping spike lowered the barrier for holes to populate the quantum well at the valence band discontinuity, and an Sb ␦-doping reduces the doping requirement of the n-type bulk Si by producing a deep n ϩ well. Samples studied from the as-grown wafers showed no evidence of negative differential resistance ͑NDR͒. The effect of postgrowth rapid thermal annealing temperature was studied on tunnel diode properties. Samples which underwent heat treatment at 700 and 800°C for 1 min, in contrast, exhibited NDR behavior. The peak-to-valley current ratio ͑PVCR͒ and peak current density of the tunnel diodes were found to depend strongly on ␦-doping placement and on the annealing conditions. PVCRs ranging up to 1.54 were measured at a peak current density of 3.2 kA/cm 2 .
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Full-band simulations of indirect, phonon assisted, interband tunneling are used to calculate the current–voltage response of a low-temperature molecular-beam-epitaxy-grown silicon tunnel diode with delta-doped contacts. Electron confinement in the contacts results in weak structure in the current–voltage characteristic. The structure is lost when finite lifetime effects are included. The approach uses the nonequilibrium Green function formalism in a second-neighbor sp3s* planar orbital basis.
We present the characteristics of uniformly doped silicon Esaki tunnel diodes grown by low temperature molecular beam epitaxy (= 275 C) using in situ boron and phosphorus doping. The effects of ex situ thermal annealing are presented for temperatures between 640 and 800 C. A maximum peak to valley current ratio (PVCR) of 1.47 was obtained at the optimum annealing temperature of 680 C for 1 min. Peak and valley (excess) currents decreased more than two orders of magnitude as annealing temperatures and times were increased with rates empirically determined to have thermal activation energies of 2.2 and 2.4 eV respectively. The decrease in current density is attributed to widening of the tunneling barrier due to the diffusion of phosphorus and boron. A peak current density of 47 kA/cm 2 (PVCR = 1 3) was achieved and is the highest reported current density for a Si-based Esaki diode (grown by either epitaxy or by alloying). The temperature dependence of the current voltage characteristics of a Si Esaki diode in the range from 4.2 to 325 K indicated that both the peak current and the excess current are dominated by quantum mechanical tunneling rather than by recombination. The temperature dependence of the peak and valley currents is due to the band gap dependence of the tunneling probability.
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