Electrical and Optical Properties of n-Type Indium-Doped CdTe/Mg_0.46Cd_0.54Te Double Heterostructures

CdTe/Mg_0.46Cd_0.54Te double heterostructures with n-type In doping concentrations, varied from 1 × 10¹⁶ to 7 × 10¹⁸ cm^-3, have been grown on InSb substrates using molecular beam epitaxy. Secondary ion mass spectroscopy measurements show strong diffusion of In from the InSb substrate to the CdTe buffer layer, while the In concentration is constant in the CdTe layer between the two Mg_0.46Cd_0.54Te barrier layers. Capacitance-voltage measurements show that the dopants are 100% ionized for the doping concentration range from 1 × 10¹⁶ to 1 × 10¹⁸ cm ^-3. The carrier lifetime decreases with increasing doping concentration (from 0.73 μs for an unintentionally doped sample to 0.74 ns for a 1 × 10¹⁸ cm^-3 doped sample) due to the decrease of both radiative and nonradiative lifetimes. Decent carrier lifetimes are achieved (∼100 ns) between 1 × 10¹⁶ and 1 × 10¹⁷ cm^-3 doping levels, which is beneficial for developing n-type monocrystalline CdTe solar cells, photodetectors, and other optoelectronic devices. The strongest photoluminescence intensity is observed when the doping concentration is 1 × 10¹⁷ cm ^-3, which corresponds to the highest internal quantum efficiency.