Structural features of Ge(Ga) single crystals grown under conditions simulating the microgravity perturbation factors

Abstract

Peculiarities of the real structure of Ge(Ga) single crystals grown under external mechanical perturbations of the crystallization process simulating actual microgravity environment aboard spacecrafts were investigated by X-ray topography and diffractometry methods, etching analysis and spreading resistance measurements. The applied perturbations included vibrations and variations of growth facility orientation with respect to the direction of gravity force. It has been shown that microinhomogeneity of the crystals grown is defined not only by formation of dopant growth striations at peculiar vibrational perturbations of a melt, but also by specific features of dislocation structure of crystals related with the formation of small angle boundaries, slip bands and other inhomogeneities in dislocation distribution.

Growth striations and dislocations in highly doped semiconductor single crystals

“…In this case, there is a significant decrease in intensity of a natural convection and there is no formation of growth striations [1,3,9]. As a result, the unique crystals have been obtained with substantially different in structure parts: in one part (the seed grown by the Czochralski method with the dislocation density N D $10 2 cm À2 ) the growth striations are the dominant type of defects and in another one (the regrown crystal with the density of dislocations up to 10 4 cm À2 ) the dislocations are.…”

“…Therefore, the lattice period of the In 1Àx Ga x As compound may be written as a(x)=(6.0585-0.4053x) Å . At small Ga concentrations the lattice strain coefficient is g=3.7 Â 10 -24 cm 3 and for the amplitude of the composition variation in the growth striations we obtain DC=f/g=1.07 Â 10 19 cm -3 . Thus from the obtained estimations, we conclude that the variation of the Ga concentration in the growth striations is at least $50% of the average Ga concentration in the crystal.…”

“…Such concentration inhomogeneities reflect the features of heat and mass transfer near the crystallization front and currently represent a major source of information on various perturbations of the crystallization process [2,3]. Therefore, quantitative data on the amplitude and spatial characteristics of composition fluctuations are important not only for the development of efficient methods to improve the crystal homogeneity, but also for analyzing of complex crystallization processes, in particular, under microgravity conditions aboard spacecrafts.…”

Concentration and structure inhomogeneities in GaSb(Si) single crystals grown at different heat and mass transfer conditions

“…They are curved and have configurations typical for dislocations (see for example Ref. [20]). The dislocation density N D considerably increases up to 10 4 cm À2 at the starting stage of crystallization process (Fig.…”

Some results of the growth of semiconductor crystals in microgravity conditions (to the 50th anniversary of Yuri Gagarin’s flight into space)

“…Then, a noticeable influ ence of vibrations and change in the growth axis of the crystals relative to the gravity force vector on the uni formity of crystals was established. It manifested itself in the appearance of growth striations, in generation of slip bands and low angle boundaries, as well as micro inclusions and characteristic dislocation and impurity distributions over the ingot diameter [13][14][15].…”