Photoreflectance spectroscopy of semiconductor device active regions: quantum wells and quantum dots

Photoreflectance spectroscopy is presented as a powerful tool of the investigation of different kinds of low dimensional semiconductor structures being a fundamental part of modern electronic or optoelectronic devices. The derivative nature of the modulation spectra gives high sensitivity of the method for optical transitions including those with nominally weak oscillator strength, like indirect in the real space or parity forbidden ones, and allows to investigate small volume objects like quantum dots. This short review includes results concerning single quantum wells of new material system like InGaAsN/GaAs, coupled quantum wells of two different material systems (GaAs/AlGaAs and InGaAs/GaAs) and several InGaAs/GaAs quantum dot structures.