Theoretical analysis of peak-to-valley ratio degradation caused by scattering processes in multi-barrier resonant tunneling diodes

A theoretical approach to resonant tunneling phenomena in multibarrier heterostructures is developed and successfully applied to the GaAs/AlGaAs triple-well resonant-tunneling diode. By introducing both the Hartree self-consistent field model and the scattering broadening model in the conventional formula, the mechanism for the P/V (peak/valley) current ratio degradation is quantitatively analyzed. The calculated results reveal that electron buildup in the first well shifts an injection level, resulting in a large decrease in second peak current with decreasing temperature. The calculated temperature dependence is in good agreement with experimental data. It is further found that the ratio of the scattering broadening Γ_s to the intrinsic broadening Γ_i is the main factor which determines the degradation of the P/V current ratio. As this ratio increases and exceeds unity, the P/V ratio steeply decreases. In a comparison of the calculations and experimental data, Γ_s is estimated to be approximately 2.5 MeV, which agrees well with the value roughly evaluated from the momentum relaxation time due to LO-phonon scattering