Use the geometric junction diode to model IC-based standard silicon diffused diodes, Schottky barrier diodes, and Zener diodes. The geometric parameter lets you specify pn junction poly and metal capacitance dimensions for a particular IC process technology.
Use the nongeometric junction diode to model discrete diode devices such as standard and Zener diodes. The nongeometric model lets you scale currents, resistances, and capacitances using dimensionless area parameters.
The Fowler-Nordheim diode defines tunneling current flow through insulators. Use it to model diode effects in nonvolatile EEPROM memory.
Star-Hspice Manual - Release 2001.2 - June 2001