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.