Nanotechnology, internal mechanical stresses, optical and electronic properties of nanostructures with germanium films on indium phosphide substrates

Nanostructures with germanium films on semi-insulating indium phosphide substrates were prepared by thermal deposition in vacuum of 10−4 Pa at different film growth rate (0.08–0.675 Ǻ/sec). The substrate thickness was the same for all heterosystems (300 μm). The substrate temperature was about 300 °C (296–312 °C), and was kept constant during the growth of the film. To study heterosystems, a set of experimental methods was used: classical light absorption spectroscopy, modulation electroreflectance spectroscopy, measurement of internal mechanical stresses in a film along the bend of heterosystems measured on a profilometer. The value of the mechanical stresses was also determined from the absorption and electroreflectance spectra. Tails of the density of states in the band gap of germanium films are detected. The value of the characteristic energy Δ and the broadening parameter of the electroreflectance spectrum depended on the manufacturing condition of heterosystems (deposition rate of film and its thickness). The most perfect films were obtained at a higher deposition rate of 0.675 Ǻ/s. Its thickness was 0.67 μm, and the deposition temperature was 296 °C.