High peak-to-valley ratios observed in InAs/InP resonant tunneling quantumdot 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 [I(V)] characterist ics was obtained up to a point above the temperature of liquid nitrogen. Th ese features were observed in measurements on low-density QD stacks, in whi ch 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 ze ro-dimensional emitter. Electrons easily fill the upper dot, whereas tunnel ing through the entire structure is only allowed when two states in the dot s align energetically, resulting in sharp resonant tunneling peaks with hig h peak-to-valley ratios. (C) 2001 American Institute of Physics.