Symmetric Si/Si_1-xGe_x electron resonant tunneling diodes with an anomalous temperature behavior

We report the fabrication of symmetric, n-type resonant tunneling diodes grown by rapid thermal chemical vapor deposition in the Si/Si _1-xGe_x material system. Up to four resonant features were observed for both positive and negative bias. This is the first time that such highly symmetric features are reported for electron resonant tunneling in the Si/SiGe material system. A peak-to-valley ratio of 2 was achieved at a temperature of 4 K and resonances were observed up to 240 K. An additional peak is observed at low voltages exhibiting an anomalous temperature behavior, disappearing at temperatures below 50 K. Models involving phonon absorption or emitter quantization are proposed to explain this behavior.