Conductance fluctuations in a double-barrier resonant tunneling device

We have investigated conductance fluctuations due to tunneling through impu rity states in the quantum well of a double-barrier resonant tunneling devi ce. The impurity States are donor-related and are associated with a low-den sity Si delta -doping layer incorporated into the center plane of the quant um well. At constant temperature, the relative amplitude of the conductance fluctuations is determined by the absolute number of donor impurities in t he well and is found to scale, as (SNd)(-1/2), where N-d is the areal densi ty of donor atoms in the well, and S is the area of the device. The typical voltage period of the fluctuations is determined by the larger of kT or th e natural linewidth of the state. There is excellent quantitative agreement between the experimental results and an existing theoretical model for con ductance fluctuations in this type of system.