High peak-to-valley ratios observed in InAs/InP resonant tunneling quantum dot stacks

Resonant tunneling was observed through single InAs quantum dot (QD) stacks embedded in InP barriers with peak-to-valley ratios as high as 85 at 7 K. Negative differential resistance in the current–voltage $\mathrm{[I(V)]}$ characteristics was obtained up to a point above the temperature of liquid nitrogen. These features were observed in measurements on low-density QD stacks, in which a macroscopic ohmic contact covered less than 150 QD stacks. Due to the design of the structure, the upper QD in the stack has the function of a zero-dimensional emitter. Electrons easily fill the upper dot, whereas tunneling through the entire structure is only allowed when two states in the dots align energetically, resulting in sharp resonant tunneling peaks with high peak-to-valley ratios.