A new optico‐acoustic phenomenon in germanium is reported. A change in the lattice constant (crystal dilatation) is observed when excess pairs of current carriers have been introduced into the sample by monochromatic illumination. The method of measurement enables one to detect small vibrations of the sample with amplitudes down to 10−11 cm. The effect has been measured in the range from 80 to 1780 cps, and shows no dependence on frequency. The ratio of relative change of the lattice constant to the carrier pair concentration has been estimated to be about 7 × 10−24 cm3 which is in satisfactory agreement with the value predicted by theory. Some features of spectral response of the effect can be explained in terms of 〈100〉 exciton states with relatively long apparent lifetimes.

Partially relaxed InGaAs/GaAs heterostructures with a small lattice mismatch have been studied by means of atomic force microscopy and high-resolution x-ray diffractometry. Additionally, electron-beam induced current in a scanning electron microscope and transmission electron microscopy have been employed to investigate misfit dislocations formed at the (001) heterostructure interface. The measurements revealed a direct correlation between the surface crosshatched morphology and the arrangement of interfacial misfit dislocations. The reciprocal lattice mapping and the rocking curve techniques employed for the samples aligned with either the [ 110] or the [110] crystallographic direction perpendicular to the diffraction plane revealed anisotropic misfit strain relaxation of the InGaAs layers. This anisotropy results from an asymmetry in the formation of the α and β types of misfit dislocations oriented along the [ 110] and [110] directions, respectively, which differ in their core structures. The misfit strain anisotropy causes a distortion of the unit cell of the layer and lowers its symmetry to orthorhombic.

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