Numerical Modeling of Surface Effects in RF Switching PIN Diodes

Surface conditions of PIN diodes influence the overall carrier lifetime of the device and hence its microwave and RF resistance, and are becoming more important with the creation of new applications of PIN diodes for 5G reconfigurable antenna structures and reconfigurable electronics. This paper builds on previous work and uses a discretized version of the PIN diode with each element containing a SPICE-compatible PIN diode model. Each element in this discretized model has a carrier lifetime that can be varied, allowing both bulk and surface effects to be modeled. Simulations of a PIN diode suitable for microwave and RF switching are performed, with the results showing the variation of resistance and effective carrier lifetime as a function of the surface carrier lifetime. The model is then applied to a series reflective PIN diode switch; the model shows that the insertion loss of the switch may vary by several tenths of a dB depending on surface conditions. Simulations also show the core region of the PIN diode experiencing a higher temperature than the surface due to increased current density in this region.