At 210 nm, the shortest wavelength/highest frequency LED seems to be composed of a Aluminum Nitride junction (according to this article).

I was wondering, what would the Vf (forward voltage) be of such a diode. I can't seem find any information on deep UV diodes and their respective Vfs (this source claims 7.5V max for a 250nm diode).

Aside from just stating a number (or an approximate number) is there any way (or approximate way) or calculate a diode's Vf vs peak wavelength (perhaps via some form of interpolation of existing diode Vfs)?

  • \$\begingroup\$ Probably it is not stated anywhere because these diodes are not commercially available. Their power output and efficiency will certainly be extremely small. Anyway, the forward voltage has to be greater than the band gap and this is a material property, but apart from that it is dependent on device characteristics and forward current. Either acquire (i.e., make or have made for you) a diode like this and measure it yourself, or wait until they become commercially available (if ever) and then look at the datasheet. \$\endgroup\$ Commented Jun 7, 2015 at 15:16
  • \$\begingroup\$ @OleksandrR. I get that there is likely no publication regarding forward voltage. I was hoping for an extrapolation based on physics/interpolation based on data. I tried myself to not much avail (based on photon energy). I don't think making an Aluminum Nitride diode is exactly doable at home, just saying... \$\endgroup\$
    – initramfs
    Commented Jun 7, 2015 at 15:19
  • \$\begingroup\$ Well, if the device characteristics are basically undefined, your only point of reference is the bandgap, as I said in my comment above. This is a lower bound for the forward voltage. For AlN (please correct your question title, by the way) it is a bit more than 6 volts. \$\endgroup\$ Commented Jun 7, 2015 at 15:22
  • \$\begingroup\$ @OleksandrR. I never said they were undefined. The 210 nm diode refers to a specific crafted diode in which there are research papers available for (paid to download however). "A bit more than 6 volts" helps but doesn't explain the reasoning behind the deduction (care to show how that is derived in an answer)? The point is to: a) see if the specific Aluminum Nitride material causes any interesting changes in forward voltage; b) see if such a cutting-edge diode requires something beyond what would normally be needed (due to inefficiencies perhaps). \$\endgroup\$
    – initramfs
    Commented Jun 7, 2015 at 15:30
  • \$\begingroup\$ In the paper they state that the forward voltage for a 20 mA forward current was 37 V for a MIS-structured diode and 45 V for a PIN-structured one. The hole mobility especially was rather small, although they go into more detail about the electrical characterization in the paper. Since it seems you are asking about this particular diode, does that answer the question? \$\endgroup\$ Commented Jun 7, 2015 at 19:10

1 Answer 1


The reference for the 210 nm diode is:

Yoshitaka Taniyasu, Makoto Kasu, and Toshiki Makimoto, "An aluminium nitride light-emitting diode with a wavelength of 210 nanometres", Nature 441, 325 (2006) [doi:10.1038/nature04760]

In this paper, the authors state that they constructed diodes having both a MIS and a PIN structure. The forward voltages for 20 mA forward current were 37 and 45 V, respectively, although the operating current (to produce 0.02 µW of 210 nm emission) was 40 mA, not 20 mA, and they don't directly state the forward voltage for this condition. The large forward voltages were (seemingly, without having checked it too rigorously) the result of having to drive such a large current through the device given the rather low hole mobility, which was around 30 cm^2 V^-1 s^-1 at room temperature.

The external quantum efficiency was stated to be of the order of 0.000001%.


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