Investigations of Asymmetric Spacer Tunnel Layer Diodes for High-Frequency Applications

A complete description of physical models for fabricated asymmetric spacer tunnel layer (ASPAT) diodes is reported in this paper. A novel In0.53Ga0.47As/AlAs design is presented and compared to the conventional GaAs/AlAs material system. For both material schemes, physical models were developed based on experimental measurements. Simulated dc characteristics of the devices are given for both planar- and back-contacted structures to highlight the impact of spreading resistance on device behavior. Furthermore, full S-parameter derivations from numerical simulation for tunnel diodes are demonstrated for the first time on the basis of quantum-mechanical ac modeling of the capacitance-voltage and conductance-voltage performances of these ASPAT diodes. A negligibly small difference between measured and simulated zero-biased intrinsic capacitances is observed (i.e., ≤ 0.2 fF). These are beneficial for accurate predictive models for device characteristics. In addition, key parameters which can be extracted from simulation results are obtained to aid in the development of millimeter-wave/terahertz applications of these types of heterostructure tunnel devices.