Optical spectroscopy of n-CdTe single crystals doped with Ge in the region of the fundamental optical transition E0

In this work optical (reflection spectra, transmission spectra) studies of n-CdTe single crystals doped with germanium with a concentration of NGe = (2 - 10) 1024 m-3 with a resistivity ρ = 104 Ohm cm - 5∙106 Ohm cm in the spectral range of 800 nm - 1100 nm were performed and photoluminescence spectra of n-CdTe single crystals doped with germanium with a concentration of NGe = (2 - 10) 1024 m-3 at a temperature of 77 K were measured when excited by laser (electromagnetic) radiation with an electromagnetic wavelength of 660 nm in the energy range of 1.3 eV - 1.65 eV. The following results were obtained: it was determined that the energy of the fundamental optical transition E0 for n-CdTe single crystals doped with germanium at T = 300 K is 1.459 eV; it was determined that the fundamental optical transition E0 for n-CdTe single crystals doped with germanium at T = 77 K is 1.580 eV; the temperature coefficient of change of the band gap width of n - CdTe single crystals doped with germanium with a concentration of NGe = (2 - 10) 1024 m-3 with a resistivity ρ = 104 Ω∙cm - 5∙106 Ω∙cm, which is equal to - 5.426⋅10-4 eV/K; the relationship between the fundamental optical transition energy E0 for n-CdTe single crystals doped with germanium and the temperature T in the temperature range 77 K ≤ T ≤ 300 K was established: E0(CdTe:Ge)=1.580 eV - 5.426⋅10-4 (T-77 K); the optical absorption spectra of the studied materials were constructed (ln(I0/I) = f(λ)); the energy relaxation time τ and the effective optical mobility of free charge carriers for n-CdTe single crystals doped with germanium were estimated; it was shown that the studied crystals have high (detector) quality, which is decisive for the manufacture of highly sensitive and high-resolution ionizing radiation sensors; the practical value of the obtained results consist in determining the electronic and physical parameters of the technically important semiconductor CdTe doped with germanium.