Not all diodes are the same for leakage due to the geometry and passivation of the Si dielectric barrier surface encapsulation, which is < 1um thick.
All diodes are thermal sensors with voltage when forward biased (NTC) and current sources with leakage current when <= 0V. Above 300 'C this leakage power poses a threat due to the much higher heat density and higher thermal resistance, (if applied with reverse voltage)
ref:
https://www.researchgate.net/public..._surface_leakage_reverse_current/figures?lo=1
Here is a low leakage Si diode.
Plastic SMD package
• Low leakage current: typ. 3 pA @ 25'C
If you need leakage current to be constant, make an SMD oven above room temp with a thermistor, regulator,10 mW SMD resistor all attached to the diode with styrafoam insulation. I've done this to make a cheap XTAL OSC. into an OCXO.
Keep in mind if
forward biased, 200 mV/100 nA = 2 Gohms equiv
I suspect the
Space Charge Limited (SCL) model of this
Poole-Frenkel (PF) effect advanced by (heavens to)
Murgatroid and Boole are such that my hunch is the equivalent circuit is constant RC varicap. The Voltage-controlled capacitance or Varicap effect is found in all diodes created by the reverse bias E-field effect to makes the leakage resistance and C constant at a fixed Temp. Tau=V
R/I
R * C might be temporarily constant while reverse leakage increases and capacitance reduces with increasing reverse voltage until the temperature changes.
But you might find the answer in this
thesis. (TL;DR)
The plastic SMD chip is black to block light which is another source of leakage current from the
photo-electric effect in all diodes, transistors and IC's.