Accurate Modeling of Double Barrier Resonant Tunneling Diodes

A program has been developed that can model the static characteristics of Double Barrier Resonant Tunneling (DBRT) diodes. This device can be considered to consist of the actual barrier structure and two reservoirs from which electrons can tunnel. Under bias one reservoir will be accumulated, the other one depleted and electrons will tunnel mainly from the former to the latter. The accumulation region provides the supply of tunneling electrons while the depletion region absorbs most of the bias voltage, so both regions have a strong influence on the device characteristics. A major problem in modeling DBRTs is the connection of the reservoirs to the barrier structure, another one is modeling the reservoirs themselves, in particular the accumulation region. Here part of the electrons is in three-dimensional states and part is confined in two-dimensional subbands. Tunneling can be partly incoherent due to interface roughness and phonon scattering. It is also important to include the charge in the well because it has a noticeable effect on the I-V and C-V characteristics as well as the noise properties. In this program all these considerations are taken into account. The model enables one also to model the static I-V and C-V characteristics of different structures. From these also the microwave noise and small-signal impedance can be calculated. The frequency range is limited to the frequency where quantum-mechanical tunneling times start to play a role.