We created a PADS pcb symbol for the BFT25 as a diode. It's much less confusing on schematics.
The c-b junctions of transistors tend to be very low leakage diodes, lots better than things born to be diodes. The smaller the junction, the better, usually. I recall that a 2N4402 leaks under a picoamp.
You can buy a PAD-1, a 1 pA spec'd leakage diode, for a couple of dollars. It's actually a jfet with the source and drain connected. The channel resistance winds up in series with the gate diode junction, ballpark 2K ohms. For 30 cents, you can buy the BFT25 and get roughly
20 fA leakage and very low series resistance.Glass-packaged diodes leak when light hits them. That can be confusing.
John