Si/SiGe electron resonant tunneling diodes with graded spacer wells

Resonant tunneling diodes have been fabricated using graded Si(1-x)Ge(x) (x=0.3 -->0.0) spacer wells and strained Si(0.4)Ge(0.6) barriers on a relaxed Si(0.7)Ge(0.3) n-type substrate which demonstrates negative differential resistance at up to 100 K. This design is aimed at reducing the voltage at which the peak current density is achieved. Peak current densities of 0.08 A/cm(2) with peak-to-valley current ratios of 1.67 have been achieved for a low peak voltage of 40 mV at 77 K. This represents an improvement of over an order of magnitude compared to previous work. (C) 2001 American Institute of Physics. (DOI: 10.1063/1.1381042