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HgCdTe energy gap determination from photoluminescence and spectral response measurements

Murawski Krzysztof, Kopytko Małgorzata, Madejczyk Paweł, Majkowycz Kinga, Martyniuk Piotr

Metrology and Measurement Systems

2023

Vol. 30, nr 1

183--194

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.

Study on high signal-to-noise ratio (SNR) silicon p-n junction photodetector

Fu X.S., Yao S.Y., Xu J.T., Lu Y., Zheng Y.G.

Optica Applicata

2006

Vol. 36, nr 2-3

421-428

On the basis of n-type single-crystal (100) silicon substrate, a silicon p-n junction photodetector has been successfully developed. Three methods to improve photoresponse signal-to-noise ratio (SNR) were profoundly studied: the p-n junction depth was optimized to enhance the spectral responsivity within the wavelength range of 500-600 nm, an antireflection layer with the appropriate thickness was added to reduce the reflected light and enhance the sensitivity, the adjustment technique of spectral band response was adopted to remove the noise signal with normal silicon absorptive wavelengths. Eventually, the spectral responsivity SNR can be over 104 at 500-600 nm while the peak of spectral responsivity is 0.48 A/W at about 520 nm. After being optimized, silicon p-n junction photodetectors, which possess the properties of lower dark current, higher sensitivity, shorter response time and larger SNR, can be achieved.