The atomic perfection of interfaces and local impurity distribution are important parameters in the control of low dimensional semiconductor systems. Over the past few years photoluminescence excitation spectroscopy has proved to be of immense value in the detailed characterisation of such systems. This is especially the case for the GaAs/AIGaAs material technology in which tunable dye lasers can readily supply the variable wavelength excitation source needed for such work.

However this form of characterisation is much more difficult for semiconductors with smaller energy gaps e.g. the ternary InGaAs or many materials in the important antimonide based system. No readily available dye lasers exist which can be used to resonantly excite the semiconductor.

We have overcome this difficulty by using Fourier Transform Optics to source the excitation. We have successfully observed excitation spectra from InGaAs/InP and InGaAs/GaAs quantum well systems. The multiplex nature and high optical throughput of the Fourier Transform spectrometer yield high quality spectra with short measurement times.

In this paper we review the experimental technique and demonstrate its enormous potential for “low” gap semiconductors. We illustrate the technique by describing its application to various quantum well systems.