Temperature-dependent photoluminescence (PL) spectroscopy is a powerful optical method for characterizing materials. PL can be used to identify defects and impurities in Si and III-V semiconductors, as well as determine semiconductor bandgaps. At room temperature, PL emission is usually broad—up to 100 nm in width. When samples are cooled, structural details may be resolved; a small spectral shift between two samples may represent a difference in structure. For cooling, two types of cryostat typically are used: a cryostat using liquid N2 or liquid He, or a closed-cycle cryostat in which cryogenic liquid is included as part of the cooling system. The cooled sample is excited by a laser, and the PL is coupled to a spectrometer via an optical interface. In this Technical Note, sample data are shown from a highresolution PL system.
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