Ge rich Esaki diodes with high peak to valley current ratios

We report on current voltage characteristics from Ge rich Si/SiGe/Si p+-i-n+ interband tunnelling diodes epitaxially grown on highly resistive Si(001) substrates. A maximum peak to valley current ratio of 5.65 was obtained at room temperature for a diode containing a Si0.55Ge0.45 alloy layer. The latter value can be further increased to 7.6 at 5 K. A simple estimation of the maximum oscillation frequency demonstrates the potential of these devices as high speed oscillators. The Ge concentration can be further increased by incorporation of self-assembled Ge islands in the intrinsic region. A careful optimization of the intrinsic layer structure leads to a maximum peak to valley current ratio of 2.65 at room temperature. The obtained device parameters are promising for future digital applications.