Group Demonstrates In-situ Photoluminescence Measurement System Within MOCVD Reactor

Laytec collaborated with Professor Dirk Rueter´s group at University of
Applied Sciences Ruhr West to demonstrate the first quasi-continuous real-time
photoluminescence study of growing InGaN LED structures inside an MOVPE
production reactor. Room temperature wafer-based photoluminescence (PL)
measurements are known to offer excellent predictors of the emission wavelength
and intensity of later LED devices. The group recently demonstrated a prototype
in-situ PL system operating simultaneously with a LayTec Pyro 400 within a
commercial multi-wafer MOCVD reactor.

They indicated that even at an early stage of the growth of the active
region the in-situ spectra can predict the photoluminescence emission
wavelength of the structure at room temperature. The researchers demonstrated
an accuracy of this predicted wavelength of ± 1.3 nm (2σ) and concluded
that the technique seems suitable for closed-loop control of the emission
wavelength of InGaN LEDs already during growth.

They were able to obtain the PL spectra of a GaN template during buffer
growth at 1058 °C wafer temperature during growth of an LED structure. They
employed a single laser shot through a complex fiber optical system to get a
sufficient number of 1×103 photons per spectrometer channel in the PL signal
in-situ.

They found an excellent correlation between in-situ and ex-situ wavelengths
from the 2nd to the 5th completed quantum well (QW) with the resulting emission
of the finished LED wafer at room temperature. They concluded that the
method’s accuracy opens the way for in-situ prediction and even feedback
control of the LED emission wavelength already during growth of the first QWs
of a MQW structure. The group published the results in the Journal of Crystal
Growth
.

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