Separation of the e1 and E1 Interband Transitions near 2 eV in Germanium by Thermoabsorption

By thermoabsorption of Ge thin films (thicknesses 300, 500, and 520 Å, modulation frequency 12.5 Hz, modulation depth δT ≤ 4 K) the interband transitions e1 and E1 in the spectral range near 2 eV are investigated including the transitions with spin–orbit splitting. It is possible to separate these transitions on account of their significantly different temperature dependences: de1/dT = −(5.47±0.02) × 10−4eV/K and dE1/dT = −(3.89±0.02) ×× 10−4 eV/K. The spectral shift divergence overcompensates the Lorentz broadening of the peaks so that their resolubility becomes better at higher mean temperatures. The energies for the transitions extrapolated to 295 K and corrected as to give bulk results are e1 = 2.107 eV, e1 + Δ = 2.294 eV, E1 = 2.134 eV, and E1 + Δ1 = 2.314 eV.