Try buying surplus night vision goggles, or another component that has the device you want. You might be able to scavenge parts...
Just a thought G --- Paul Lowrance <[EMAIL PROTECTED]> wrote: > More discoveries. It appears a HgTe photodiode is > just about the ultimate > material for this research. It has a band gap of > zero eV! Various amounts of Cd > (Hg[x-1]Cd[x]Te) increases the band gap to whatever > value you want. Here are > some interesting quotes --> > > Quote #1 from WikiPedia: > --- > Owing to its cost, the use of HgCdTe has so far been > restricted to the military > field and infrared astronomy research. Military > technology depends on HgCdTe for > night vision. In particular, the US air force makes > extensive use of HgCdTe on > all aircraft, and to equip airborne smart bombs. A > variety of heat-seeking > missiles are also equipped with HgCdTe detectors. > --- > > Quote #2 from WikiPedia: > --- > The main limitation of LWIR HgCdTe-based detectors > is that they need cooling to > temperatures near that of liquid nitrogen (77K), > ***TO REDUCE NOISE*** due to > thermally excited current carriers > --- > > Note the bold text in Quote #2. This material is so > noisy they need to cool it > to 77K, otherwise the voltage noise is incredible > ... bingo! > > This is so ironic. Why are most desirable things > come at such high cost? > Everyone loves ice cream, but the calories. I would > give just about anything to > experiment with a p-n HgTe photodiode, but it's > ridiculously expensive. Would > they even sell it to me? > > Furthermore, this material has ultra wide bandwidth. > > Mercury(II) cadmium(II) telluride (HgCdTe): > http://en.wikipedia.org/wiki/HgCdTe > > band gap image diagram: > http://en.wikipedia.org/wiki/Image:HgCdTe_Eg_vs_x.PNG > > > Regards, > Paul Lowrance > > > > > Paul Lowrance wrote: > > 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 > > > > ____________________________________________________________________________________ The fish are biting. Get more visitors on your site using Yahoo! Search Marketing. http://searchmarketing.yahoo.com/arp/sponsoredsearch_v2.php
