Abstract.
The description of the automated hardware and software
complex for measuring the boundary frequency of modulation and determining the
quantum efficiency of separate spectral components of the full
electroluminescence spectrum of light-emitting diodes is presented. The
principle of operation of the complex is based on the accumulation of the
measuring results of the LED emission spectrum from the output of the
OceanOptics USB2000+ spectrometer when passing through the LED current pulses
of a given amplitude and frequency and subsequent allocation of individual
spectral components from the total spectrum. The complex is tested on
commercial green InGaN LEDs with quantum wells. Dependences of the boundary
frequency of modulation and the level of the spectral components on the
amplitude of the current pulses are given. Estimations of the lifetime of
charge carriers for radiative and nonradiative recombination in the current
range of 10 μA–10 mA are obtained. It is established that the lifetime
of charge carriers in nonradiative recombination decreases monotonically over
the entire range of currents, and the lifetime of charge carriers in radiative
recombination forming the long-wavelength wing of the electroluminescence
spectrum reaches saturation in the region of high currents, which is explained
by saturation of the levels of radiative recombination in quantum wells with
growth injection current. The developed hardware and software and technique of
assessment of recombination parameters of heterojunction LEDs with quantum
wells can be used as for the purposes of diagnostics of quality of LEDs, and in
case of working off of constructional technology solutions during creation of
new light-emitting structures.
Key words: LED,
electroluminescence, spectral quantum efficiency, boundary frequency of
modulation, radiative recombination, nonradiative recombination, lifetime of
charge carriers.
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