Long‐term Crystal Growth under Microgravity during the EURECA‐1 Mission (II) THM Growth of Sulphur‐doped InP

Abstract

Long-term cryst,al growth expcrirnents were successfully performed under microgravity conditions diiririg the first flight of the unmanned EURECA-1 mission in the automatic mirror furnace (AMF). Two crystals of sulphur-doped InP with [OOl] and [lll] orientation respectively were grown from indiinn solution by the travelling heater method (THM). The absence of time dependent buoyancy-driven convcction is documented by the lack of type I striations in the space-grown crystals. The sulphur conccntration is measured by spatially rcsolved photoluminescelice. As exp m;tcrosegrcgation can be described by a pure diffiisiori-controlled model which is in good agrccment wit,h the findings from the first German spacelab rriission D1. Compared to the earth-grown refer-(:rice s:trnples, both of the space-grown InP crystals show strong disturbances such as inclusions and type I1 striat,ions. The morphological instabilities arc siniilar to growth disturbances already known from the space-grown MD-ELI-01 from the D1 mission.

Macrosegregation in the growth of doped III‐V‐semiconductors from the solution

“…Each of the highest concentration values corresponds to a undisturbed crystal area because the dopant content inside the trace of an inclusion is always low [5]. Therefore the segregation profiles can be fitted as the enclosing curves for the scattering values of facet and off-facet areas respectively, using eq.…”

“…Due to the huge mass differences of indium and phosphorous strong solutal effects are to be expected. All the experimental details and growth results are given in previous papers for the crystals grown during the 1 st German spacelab mission D1 [3], on board of the European satellite EURECA [4,5,6] and the Russian reentry satellite FOTON [7]. Especially the EURECA experiments demonstrated, that even under very good microgravity conditions of 10 -6 g solutal convection governs the material transport in the In -P system [5,8].…”

“…3 for the crystal AM13/1F1 from the EURECA mission as an example. The underlying microscopic picture (Nomarski interference contrast (NIC) of the chemical etched crystal slice [1,5]) shows the begin of growth period 6 where the rotation was started with 1 rpm, visible from the onset of rotational striations. The overlaid linescan resolves rotationals with concentration differences of less than 5 x 10 16 cm -3 and distances smaller than 5 µm.…”

“…The highest S concentration in the seed corresponds to 1.2 x 10 19 cm -3 . As expected from the different growth mechanism the S concentration is higher in the central facet as in the off-facet [5]. With the known S concentration of the feed The diffusion coefficient D S is determined from the space experiments.…”

“…In such an orbit the z-axis of the satellite and the growth direction of the crystals respectively point permanently to the sun. As a result the gvector turns by 360° through the liquid zone during one orbit [6,8].…”