The noise characteristics of symmetrical double barrier resonant tunneling structures were measured in two samples with a fixed well width of 50 A˚ and barrier thicknesses ofLB=8 monolayer and 10 ML, respectively. The measurement was done in the frequency range of 1 Hz–100 kHz and temperature range of 77–300 K. The noise due to the excess current in the valley region, observed in both devices, was associated with defect assisted tunneling which is a two‐step process: generation‐recombination noise due to the trapping and detrapping mechanism, and 1/fnoise due to the scattering by phonons. The current dependence of 1/fnoise contribution was investigated in the resonant tunneling and valley regions. The frequency exponent of the 1/fnoise component was found to vary between 0.9–1.1 for double barrier resonant tunneling diode (DBRTD) withLB=8 ML and 1.1–1.2 for DBRTD withLB=10 ML. This noise investigation implies that there is a difference in the physics governing the transport between DBRTD withLB=8 ML and DBRTD withLB=10 ML. ©1995 American Institute of Physics.