Si-diodes in Second World War radar & Communication equipment

Did they even _have_ silicon diodes in WWII? I remember when they announced the first transistor, some time in the early 1950's.

Thanks, Rich

Yup. Most of the WWII radar diodes were silicon point-contact types, Schottky diodes actually. The best 1943-vintage mixer parts were about as good as any packaged schottky you can buy today... 0.2 Vf, 0.2 pF, decent noise figures to 30 GHz.

The point-contact transistor was invented at Bell Labs in 1947. Most of the relevant semiconductor theory - bandgaps, hole/electron conduction, doping - was well understood by about 1940. The RadLab guys didn't develop a PN-junction diode or the transistor because their mandate was to develop radar to win the war.

John

I'd question that "was well understood" part. The description in the Buderi book makes it pretty clear that before 1940, people working with semiconductors (key being at Bell Labs) didn't have a very deep understanding of what was going on. It was only in late '39 and 40 that they got serious ideas that they could actually control what was an essentially empirically-understood phenomenon by changing the amount and type of impurity. The description of things going on then as "increasingly curious properties" of silicon doesn't seem to fit very well with "well understood." But maybe Buderi didn't do a very good job documenting that particular work, and missed the depth to which the phenomena were understood.

Cheers, Tom

Artech has never been cheap. :-) At this price, I think they figure they're appealing mainly to University technical libraries and perhaps some larger companies' internal corporate libraries... or perhaps they're thinking the market for such historical documents is quite limited, thus "necessitating" the higher price to cover their costs?

Just checking the footnotes in the radlab book, it looks like most of the serious theorizing (ie, stuff that worked) was published between

John

V(f) @ 1 mA. Result < 180 mV. Thus Ge, not Si.

Certainly. 1N23s that i had were Ge also. Lost them on some move.

Gee, John. Where do you get schottky diodes with V(f) below 0.2 V at I(f) of 1 mA? All the ones i could find were over 0.33 V and mostly

I have seen silicon schottky diodes that drop about .3 volt at 1 amp.

- Don Klipstein ( snipped-for-privacy@misty.com)

I am on a temporary setup now that does not have Acrobat, but I somewhat remember Vishay-IR STPS1L30UPBF or 1N5818 dropping maybe .35 volt at 1 amp. These are 30 volt 1 amp Schottky rectifiers.

- Don Klipstein ( snipped-for-privacy@misty.com)

Here are some curves from the RadLab book:

ftp://66.117.156.8/RadLabDiodes.JPG

ftp://66.117.156.8/RadDiode2.JPG

Your data point is dead on the point-contact Silicon diode curve.

John

A couple of fascinating books are Buderi's "The Invention That Changed The World" and Conant's "Tuxedo Park", both about the history of microwave radar, and where the money came from.

Also Bowen's "Radar Days" and the Brit story of HF radar, "Three Steps To Victory" by Sir Robert Watson-Watt, who probably saved England from the Luftwaffe.

John

One of the MIT books says that "a semiconductor triode should be possible." But that wasn't their mandate. The RadLab was disbanded in late 1945.

John

This is a silicon point-contact diode, essentially the same as the WWII parts, expect that they get to use modern, very pure silicon:

Skyworks makes some very low capacitance (below 0.5 pF) schottkies that are similar.

This is 300 mV *max* at 100 mA, so should be down there. I think the schottky curve is sorta similar to the silicon PN curve, which is 60 mV per decade of current.

I posted some WWII diode curves elsewhere, well under 200 mV at 1 mA.

Gee.

John

"JosephKKK Lunatic & Congenital LIAR "

BAT46 = 0.261 V @ 1mA

MBR745 = 0.194 V @ 1mA

For comparison

AAZ15 (Ge) = 0.230 V @ 1 mA

The 1N23 ( Silicon point contact) is 0.25 V @ 1mA

...... Phil

Rich Grise inscribed thus:

Yes ! I have some devices that were made in the mid to late 40's.

Also if I can find them I have some pre war point contact detectors that have screw terminals on the ends.

Baron.