Hi,
The following is an important consideration for those interested in the very
real upcoming technology that will capture significant continuous energy day or
night from ambient temperature (surrounding air and Earth).
Silicon and Germanium are what is called *Indirect band gap* material. This
means Si and Ge are inefficient at emitting and receiving radiation. Although
recent technology has made it possible to make Si LED's, but that's more complex.
The following link contains a very nice table of different semiconductors
showing which materials are Indirect and Direct band gap -->
http://www.chemistry.patent-invent.com/chemistry/semiconductor_materials.html
Therefore, it seems highly advantageous to perform experiments using the
following materials -->
* Indium Antimonide (InSb) 0.17 eV
* Indium Arsenide (InAs) = 0.354 eV
InSb is the best choice for capturing room temperature black body radiation. I
believe the above are direct band gap materials, which means they are efficient
at receiving and emitting radiation.
It's too bad Germanium is indirect band gap. Sure glad I discovered this before
heading out to buy various Ge diodes. :-) Tom Schum placed 32 germanium diodes
in series, which resulted in ~1 uV. What would be terribly interesting is to see
the vast difference an InSb or InAs LED would make.
It seems unrealistic to use a $108 to $175 MID-IR LED for a replicable
experiment. Very few people would spend $108 just to verify that ambient
temperature energy is capturable. People who already believe don't need it. One
almost needs to pay a skeptic to view an experiment that goes against their beliefs.
There is one alternative, and that's the $10 1550 nm LED, made of InGaAsP, but
I'm not sure present instruments could measure the effect at room temperature. I
calculate the effect would be ~100 million times less than the $175 4900 nm LED.
The presence of Ga greatly increases the band gap, unfortunately, which is why
this LED is only 1550 nm.
Regards,
Paul Lowrance
