Fast measurements of photoreflectance spectra by using multi-channel detector



Photoreflectance (PR) measurements were performed on GaAs- and GaN-based structures in the so called ‘bright configuration’ where the sample was illuminated by white light (probing beam) instead of monochromatic light as it takes place in the standard configuration, i.e., so-called ‘dark configuration’. Within this concept the whole PR spectrum can be measured/processed at the same time using a multi-channel detector (i.e., CCD camera) instead the phase sensitive lock-in detection system with the one-channel detector. In this work PR spectra for Si δ-doped GaAs structure have been measured using both the CCD detector system as well as the standard lock-in technique with the one-channel detector system. GaAs-related Franz–Keldysh oscillations, which are typical of Si δ-doped GaAs structure, have been clearly observed in PR spectra measured by using the two detection systems. In addition, the PR system with the CCD detector has been used to measure PR spectra in the UV spectral region for an InGaN/GaN/Al2O3 structure. In this case, PR resonances related to InGaN and GaN band gap absorption have been clearly observed. Using the PR system with CCD detector the time of PR measurements was reduced to few seconds for both GaAs- and GaN-based structures. It shows that the bright configuration of PR set-up with multi-channel detection system is very promising and perspective in the fast diagnostic of semiconductor structures. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)