Abstract
The spatial uniformity of GaSb- and InAs substrate-based structures containing type II quantum wells was probed by means of large-scale photoluminescence (PL) mapping realized utilizing a Fourier transform infrared spectrometer. The active region was designed and grown in a form of a W-shaped structure with InAs and GaInSb layers for confinement of electrons and holes, respectively. The PL spectra were recorded over the entire 2-in. wafers, and the parameters extracted from each spectrum, such as PL peak energy position, its linewidth and integrated intensity, were collected in a form of two-dimensional spatial maps. Throughout the analysis of these maps, the wafers’ homogeneity and precision of the growth procedure were investigated. A very small variation of PL peak energy over the wafer indicates InAs quantum well width fluctuation of only a fraction of a monolayer and hence extraordinary thickness accuracy, a conclusion further supported by high uniformity of both the emission intensity and PL linewidth.
Highlights
Photoluminescence (PL) imaging has been widely employed as a qualitative measurement method of semiconductor structures
The aim of this work is to examine the spatial homogeneity of emission (the PL peak spectral position, linewidth understood as the peak full width at half maximum (FWHM) and PL intensity) in type II quantum wells by measuring mid-infrared photoluminescence maps
Several processes may contribute to the energy emission discrepancy: the layers thickness and/or composition variation due to radial inhomogeneity of the corresponding atomic beams or substrate temperature during the epitaxial growth. It has been shown before [26, 27] and mentioned above that the emission wavelength of the discussed quantum wells (QWs) is very sensitive to the InAs thickness, whilst the GaInSb width fluctuations have a minor impact on the transition energy
Summary
Photoluminescence (PL) imaging has been widely employed as a qualitative measurement method of semiconductor structures. The near-field photoluminescence spectroscopy is at forefront, providing spatial resolution at submicronic scale in the near-infrared spectral range [1, 2]. There are, just a few reports on mapping in the midinfrared spectral range utilizing a Fourier transformed infrared (FTIR) spectrometer, regarding mainly the uniformity investigations of mercury cadmium telluride epilayers [9, 10]. No spatially resolved PL study of Dyksik et al Nanoscale Research Letters (2015) 10:402 quasi-two-dimensional structures emitting in this spectral range has been reported yet, which would be of high importance if the fabrication of devices, such as semiconductor lasers, is based on these systems
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