HgCdTe energy gap determination from photoluminescence and spectral response measurements

• Published in: Metrology and Measurement systems Vol. 30; no. 1; pp. 183 - 194
• Main Authors: Murawski, Krzysztof, Kopytko, Małgorzata, Madejczyk, Paweł, Majkowycz, Kinga, Martyniuk, Piotr
• Format: Journal Article
• Language: English
• Published: Warsaw Polish Academy of Sciences 01.01.2023
• Subjects: Blue shift; Bolted joints; Boltzmann distribution; Cut off wavelength; Distribution functions; Energy distribution; Energy gap; hgcdte; infrared detectors; Low temperature; Mercury cadmium tellurides; Photoluminescence; semiconductor energy gap; spectral responsivity; Spectral sensitivity; Temperature; Temperature dependence
• ISSN: 2080-9050; 2300-1941
• DOI: 10.24425/mms.2023.144395

The temperature dependence of photoluminescence spectra has been studied for the HgCdTe epilayer. At low temperatures, the signal has plenty of band-tail states and shallow/deep defects which makes it difficult to evaluate the material bandgap. In most of the published reports, the photoluminescence spectrum containing multiple peaks is analyzed using a Gaussian fit to a particular peak. However, the determination of the peak position deviates from the energy gap value. Consequently, it may seem that a blue shift with increasing temperature becomes apparent. In our approach, the main peak was fitted with the expression proportional to the product of the joint density of states and the Boltzmann distribution function. The energy gap determined on this basis coincides in the entire temperature range with the theoretical Hansen dependence for the assumed Cd molar composition of the active layer. In addition, the result coincides well with the bandgap energy determined on the basis of the cut-off wavelength at which the detector response drops to 50% of the peak value.