Observation of negative differential resistance in a Si/Ge_0.4Si_0.6/boron δ-doped Si heterostructure

In this paper, observation of the negative differential resistance (NDR) phenomenon in a three-terminal pseudomorphic i-Si/i-Ge_0.4Si_0.6δ-doped-Si heterostructure is reported. The proposed structure offers high hole mobility of about 2650 cm²/V·s at 77 K in the Ge_0.4Si_0.6 channel and shows a pronounced NDR property in the drain-source I-V characteristics. The measured onset drain-source voltage of the NDR region is found to be within a range of 0.9 to approximately 1.4 V, which strongly depends on the collector voltage. Real-space transfer (RST) of light holes between the channel and collector regions is shown to be responsible for the observed NDR characteristics. Experiment results and the device operation are described. In addition, the influence of the drain-collector leakage current, due to a non-ideal undoped layer, on the NDR behavior is analyzed.