Well, it's just my theory.Thanks - sounds like the trapped charge is the cause of the asymmetry. Is it roughly true then that trapped charge plays no part in conduction until the mobile charges are used up. Then they diffuse back into the bulk once the bulk carrier concentartion is sufficiently low?
That must be a real bucket size drop- may cost you a fortune- or a nano stadium.One GaAs process engineer once told me a drop converted to a gas could wipe out a stadium.
The same effect occurs in common emitters used as active loads. " Current controlled Resistance with a constant reverse Vbc voltage" Effectively identical to PD's except controlled by light current and similar to LDR's. So "cannot do" is false.If you want a resistance that varies with light, which photo diodes cannot do.
Photo diodes and photo transistors vary their current, not their resistance (which is quite high).
The safe limits are described in https://www.cdc.gov/niosh/idlh/7440382.html.He was referring to the pure gas measured in [ppb] in semi-foundries, rather than oxides or other compounds,
Revised IDLH: 5 mg As/m3
Basis for revised IDLH: The revised IDLH for inorganic arsenic compounds is 5 mg As/m3 based on acute inhalation toxicity data in animals [Flury 1921; Spector 1955]. This may be a conservative value due to the lack of relevant acute toxicity data for workers. [Note: NIOSH recommends as part of its carcinogen policy that the "most protective" respirators be worn for inorganic arsenic compounds at concentrations above 0.002 mg As/m3. OSHA currently requires in 29 CFR 1919.1018 that workers be provided with and required to wear and use the "most protective" respirators in concentrations exceeding 20 mg As/m3 (i.e., 2,000 x the PEL).]
You are right that both PH3 and AsH3 stink like hell. But nothing can beat the arsenic compound called cacodyl oxide (https://en.wikipedia.org/wiki/Cacodyl_oxide) in stink!In the fab you would likely be exposed to arsine gas
if anything. But arsine is pyrophoric so would become
atomized arsenic oxide on contact with atmosphere.
All of the process gasses are nasty to some degree,
most of them highly flammable (SiH4, PH5, AsH3, BH3)
and many self-igniting.
Arsenic concentrations in silicon ICs are very low, shot
mostly at underlayers (where low thermal diffusion
lets dopant stay put through process thermal cycles; if
you didn't care about that, you'd have used phosphorus)
and encapsulated by overglass. Usually ~ 1 - 100ppm
and tough to get at anything past the surface unless
you are consuming the silicon, atomically fine.
Now take an acetylene torch to a GaAs RFIC, you'd
get a whole 'nother level of stank.