@brundall,

"Something is amiss with this 4th terminal excuse in my opinion. I believe they may have been approached already by a prospective partner for GaAs and were 'told/asked/begged' to delay development of POET somehow so they could get in on the cheap."

This has no basis in fact and can't be investigated.  Why tack on a conspiracy theory to explain something when the simpler explanation is the one given.  Brundall, you are new to this forum so you may not realize that we have often blown small positive facts out of proportion, which has had the effect of inflating optimism.  I think your comment will have the opposite effect of generating fear and pessimism where little is warranted. 

"There's a two year statute of limitations in the courts for these kind of shennanigans is there not?"

I'm really against taking action such as bothering the IIROC or causing legal trouble for POET.  I think they are telling the truth - inconvenient as it is for us - and they need to proceed unfettered in order to get their work done.  I'm invested in this company, if you are also invested you may wish to reconsider the implications of what you are recommending.

"So you are saying that a 4th terminal is almost impossible to produce on a thyristor using current technologies? So why did Dr Taylor & co (a) not know this and (b) not use the 'easier' bicfet option from day one?"

POET isn't a current technology, that's correct.  POET (to my knowledge) is the only company trying to make a thyristor an option to use in microelectronic devices.  It's not crazy for POET to invest in developing this.  There really is a precedent for the 4-terminal thyristor:

Here is the background on the thyristor in general:

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-7/hysteresis/

Here is information on a 4-terminal version:

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-7/silicon-controlled-switch-scs/

The following (indented) is speculation on my part based on my reading, I'm not a materials or electronic engineer.  I've been thinking about why POET sought to take the thyristor path over the BICFET. 

I think that thyristors are preferable because they are extremely low energy.  They don't need energy to keep the circuit open.  Once the gate is open it remains in that state until the closed state is caused by a change in the voltage.  I think common transistors need to be kept open by maintaining the voltage - which is costly.  All of the promises about cost savings would still be relevant with a BICFET version, but I think you lose some of the energy savings (which are also cost savings in a different way) when you build your circuit with transistors like a BICFET.

Most of the errors I've read on this board have been corrected, but I am still getting the sense that people think that the technical hurdles POET has experienced are insurmountable or prove that POET was a bust from the beginning.  Also, what Suresh has called a "workaround" shouldn't be seen as some MacGyvering of a new device that amounts to hacking something new together in order to salvage the POET platform. Nothing coule be further from the truth in my opinion. In my case, I try not to form opinions which have no basis in the facts available to me. So here they are:

POET is robust, as seen in the patents.  Most of what Geoff Taylor patents when it comes to full circuits has multiple embodiments.  A couple I'll post below have thyristor versions AND BICFET versions.  Yes, Geoff thought of everything.  He's got thyristors and transistors available under the POET platform.

Here's a couple of examples of what I've been reading that shows a BICFET and 4-terminal Thyristor used together in the same device:

https://patents.google.com/patent/US20160178988A1/en?q=%22four+terminal%22&q=BICFET&inventor=geoff+w+taylor

https://patents.google.com/patent/US20160178987A1/en?q=%22four+terminal%22&q=BICFET&inventor=geoff+w+taylor

I'm not saying that the roadblock we are currently dealing with is trivial, but our situation isn't such that new devices need to be added to the POET platform in order to potentially resolve the issue.  The new build would likely involve a brand new epitaxial stack to accommodate the BICFET-based embodiment and all of the other devices (detectors, etc.) would have to be made compatible with the new stack.  It's exactly as management described, and not some conspiracy.