Fitting of photoluminescence spectra for structural characterisation of high current density resonant tunnelling diodes for THz applications

High-resolution X-ray diffraction (HR-XRD), and low-temperature photoluminescence spectroscopy (LT-PL) are used to investigate the structural properties and inhomogeneities of high current density InGaAs/AlAs/InP resonant tunnelling diode (RTD) wafer structures. The non-destructive assessment of these structures is challenging, with structural variables: well and barriers thickness and the well indium molar fraction, in addition to electronic variables such as the band-offsets being functions of strain, growth sequence, etc.. Experimental PL data are compared with simulations allowing the deconvolution of the PL spectra, that includes Type I and Type II transitions broadened by interface fluctuations on length scales smaller and much larger than the exciton. This method provides details of the non-uniformity of the epitaxial material nondestructively.