Improvement in negative differential conductance characteristics of hole resonant-tunneling diodes with high Ge fraction Si/strained Si_1-xGe_x/Si(1 0 0) heterostructure

Hole resonant-tunneling diodes (RTD) with Si/strained Si_1-xGe_x heterostructures epitaxially grown on Si(1 0 0) have been fabricated and improvement in negative differential conductance (NDC) characteristics for high Ge fraction such as x = 0.5 was investigated. It is clearly shown that SiH₄ exposure at low temperatures of 400-450 °C just after Si_1-xGe_x epitaxial growth is effective to suppress surface roughness in atomic order. In the case of the RTD with x = 0.48, NDC characteristics for 1.4-nm thick Si barriers were observed at higher temperatures around 270 K than that for 2.4-nm thick Si barriers. By increasing the Ge fraction to x = 0.58, NDC characteristics were also observed at higher temperatures around 290 K than that with x = 0.48.