Optical properties of indium-doped CdTe/MgCdTe double heterostructures

CdTe/MgCdTe double heterostructures with n-type indium doping concentrations, varied from 1×10¹⁶ cm^-3 to 1×10¹⁸ cm^-3, have been grown on InSb substrates using MBE. Capacitance voltage measurements show that carriers are 100% ionized for the doping concentrations in this range. The carrier lifetime decreases with increasing doping concentration, from 0.73 μs for an unintentionally doped sample to sub-nanosecond for a 1×10¹⁸ cm^-3 doped sample, due to the decrease of both radiative and non-radiative lifetimes. The strongest photoluminescence intensity is observed when the doping concentration is 1×10¹⁷ cm^-3. It is found that beyond this doping level, optical transitions related to defect states appear below the energy level of band to band transition.