Electrical and Optical Properties of n-Type Indium-Doped CdTe/Mg0.46Cd0.54Te Double Heterostructures

CdTe/Mg
_0.46
Cd
_0.54
Te double heterostructures with n-type In doping concentrations, varied from 1 × 10
¹⁶
to 7 × 10
¹⁸
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
_0.46
Cd
_0.54
Te barrier layers. Capacitance-voltage measurements show that the dopants are 100% ionized for the doping concentration range from 1 × 10
¹⁶
to 1 × 10
¹⁸
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 × 10
¹⁸
cm
^-3
doped sample) due to the decrease of both radiative and nonradiative lifetimes. Decent carrier lifetimes are achieved (~100 ns) between 1 × 10
¹⁶
and 1 × 10
¹⁷
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 × 10
¹⁷
cm
^-3
, which corresponds to the highest internal quantum efficiency.