Diode peak reverse recovery current
There are different SPICE parameters.. 

For example, the NXP model has TT = 3.48E-9  

Central Semiconductor has TT = 2.88E-9

Vishay 1N4148W (T154D chip) has TT = 4E-9

None of those looks much like 20ns, but I didn't look at every maker of 1N4148s. 



In any case, you may find this Matlab page useful. 


  Datasheets do not typically provide values for TT and τ. Therefore the Diode block provides an alternative parameterization in terms of Peak reverse current, Irrm and Reverse recovery time, trr. Equivalent values for TT and τ are calculated from these values, plus information on the initial forward current and rate of change of current used in the test circuit when measuring Irrm and trr.