USING A LIGHT-EMITTING DIODE AS A HIGH-SPEED, WAVELENGTH-SELECTIVE PHOTODETECTOR

A light-emitting diode (LED) can function as a wavelength selective ph otodetector. To evaluate the potential for a LED-based photodetector, we have investigated the stationary and temporal characteristics of tw o kinds of LEDs: a Zn-doped InGaN blue LED and a GaAlAs red LED. The a pplication of a high current produced two peaks on the emission spectr a of the blue LED, at 380 and 450 nm. The extinction profile of the bl ue LED was consistent with its UV-emission profile. The red LED showed an emission peak at 660 nm and an extinction peak at 620 nm. The LED- based photodetector responded within nanoseconds of the onset of the l ight impulse. The application of a reverse bias to the LED caused the time spread of the output current wave form to decrease dramatically a nd was accompanied by an increase in peak height. At a 75 V reverse bi as, the resultant pulse widths were 2.6 ns in the blue LED and 7.4 ns in red LED. (C) 1998 American Institute of Physics. [S0034-6748(98)009 11-3].