Cutoff wavelength of Hg_1-x Cd_x Te epilayers by infrared photoreflectance spectroscopy

A comparative study of cutoff wavelength is performed by photocurrent (PC), transmission, and infrared photoreflectance (PR) spectroscopies on arsenic-doped Hg1-x Cdx Te molecular beam epitaxial layers in the midinfrared spectral region. It is illustrated that (i) a shorter cutoff wavelength of PC response may be predicted by either the band gap or the energy of the half-maximum transmission and (ii) the main PR peak is coincident energetically to that of the third-derivative maximum of the PC spectrum. The mechanism behind is discussed with the aid of photoluminescence measurements. The results indicate that the infrared PR spectroscopy may serve as a contactless alternative to the PC spectroscopy for predicting the cutoff wavelength of narrow-gap HgCdTe epilayers reliably.