Abstract: An infrared LED can function efficiently as both an emitter and a detector at a common wavelength without undesirable characteristics found in avalanche diodes. The LED comprises a graded-bandgap Ga.sub.1-x Al.sub.x As semiconductor material with two semiconductive regions that form a p-n junction. The value of x (the amount of aluminum in the semiconductive material Ga.sub.1-x Al.sub.x As) is varied monotonically as the material is grown so that x decreases monotonically from a value greater than approximately 0.08 at the diode surface on the N side of the p-n junction to a value not less than zero at the diode surface on the P side of the junction. The value of x at the p-n junction is greater than 0 and less than approximately 0.08 as a result of a high initial growth temperature of at least about 930 degrees Celsius.

Abstract: An infrared LED can function efficiently as both an emitter and a detector at a common wavelength without undesirable characteristics found in avalanche diodes. The LED comprises a graded-bandgap Ga.sub.1-x Al.sub.x As semiconductor material with two semiconductive regions that form a p-n junction. The value of x (the amount of aluminum in the semiconductive material Ga.sub.1-x Al.sub.x As) is varied monotonically as the material is grown so that x decreases monotonically from a value greater than 0.08 at the diode surface on the N side of the p-n junction to a value not less than zero at the diode surface on the P side of the junction. The value of x at the p-n junction is greater than 0 and less than 0.08 as a result of a high initial growth temperature of at least about 930 degrees Celsius. A wavelength matched emitter and detector system is realized by adjusting the present diode's initial growth temperature so that its detector response curve substantially overlaps the emission curve of a second diode.