Design and analysis of GaAs/AlAs asymmetric spacer layer tunnel diodes for high-frequency detection

In the present work, we have systematically investigated the design of Asymmetric SPAcer-layer Tunnel (ASPAT) diodes using numerical modeling employing SILVACO Atlas software. After reproducing and validating physical models using experimental data obtained from fabricated ASPAT diodes, a developed SILVACO model was used to evaluate the effect of different structure designs on two key parameters, namely the junction resistance and curvature coefficient at zero bias. The impact of the variation in the spacer layers thicknesses, emitter, collector, their doping profile, and the barrier width was thoroughly explored. It was found that the spacers and the barrier thickness are the most critical design parameters affecting the junction resistance and curvature coefficient. The insertion of an In_xGa_1-xAs QW layer adjacent to the AlAs barrier, combined with the appropriate choice of spacers and AlAs barrier thicknesses, contributed to an increase in the curvature coefficient by a factor of three while maintaining a low junction resistance. The cut-off frequency of a 4 × 4 μm² ASPAT device is predicted to be > 500 GHz at zero bias. A comprehensive study is presented to guide researchers working on ASPAT devices, providing valuable prediction for appropriate design parameters toward maximizing the microwave/mm-wave device performance.