Photoelectrochemical Properties of Semiconducting Cadmium Mercury Telluride Thin Films with Bandgaps Between 1.47 and 1.08 eV

Films of Cd-rich cadmium mercury telluride (Cd_xHg_1-xTe, CMT) 0.1 to 2 µm thick were formed on conducting glass (Sn0₂) and cadmium substrates by electrochemical (potentiostatic) deposition from an aqueous bath. 1 - x ranged from 0 to 0.25. The photoresponse of CMT electrodes of n- and p-type was investigated in electrolytes containing different redox couples. In 1M polysulfide solution, the onset of photocurrents was found at −1.1V vs. SCE, independent of the optical bandgap. In the plateau range of the photocurrent potential curves, quantum yields of charge collection up to 0.45 were measured for Cd_0.9Hg_0.1Te. The long-wavelength onset of photoresponse varied with the bandgap (1.47–1.08 eV) for 1 - x between 0.01 and 0.2. The drawback of the small minority-carrier diffusion length of CMT grown by electrocrystallization can be circumvented with stacked, semitransparent thin-film electrodes. Experiments show that with such a configuration of thin CMT films grown on transparent substrates, the total photocurrent output can be increased considerably.