The nonlinearity of high-radiance light-emitting diodes

Distortion measurements have been performed on a series of Burrus-type LED's as a function of device structure, type of dopant, and dopant concentration in the active layer of devices. The results of measurements show that the total harmonic distortion (THD) in double heterostructure LED's is relatively insensitive to the type and amount of dopant in the active layer provided the ratio of the active layer thickness
d
to diffusion length
L
is less than one. For
d/L > 1
an improvement in THD is observed by about 20 dB to a value of -50 dB at 100 mA dc and 100 mA peak-to-peak modulation currents. The improvement in the linearity is attributed to the reduction of the influence of the heterostructure boundary on the minority carriers in the active layer of LED's.