The design and operating procedure of apparatus for direct microscopic measurement of step movement during crystal growth is presented. The equipment consists of a microscope for observation of growth features, a reaction cell, furnace, and gas-flow control system. The apparatus has been employed to investigate growth mechanisms operative during the deposition of germanium by dissociation of GeI2 in an open tube flow system.

A series of reproducibility tests was carried out, early in the program, using one of the production triple carbonates. The batches of coated filaments were prepared at different times from individually baH-milled suspensions of the same powder. The two coatings differed with respect to their bulk densities by 4.3%. The sample weights had a 2.2% difference, and the coating thickness variation was 2.5%. Examination of the pressure-time curves for six samples in each test batch revealed that the average peak pressures were 1.82 • 10 -~___ 0.05 • 10 -3mm and 1.83 • 10 -8_0.09 • 10 ~ mm, respectively. The corresponding average temperatures at these pressure peaks were 878 ~ and 876~ The decomposition times (see text) were 70.6 and 67.3 sec. While individual results in each batch showed deviations from the average of 1 to 5%, the difference between batches was only about 1%. The production carbonate used in these tests continued to serve as a control material with which the reliability of the over-all test equipment and procedure were checked periodically.ABSTRACT It has been found that high-resistivity AISb ingots result from the zone refining of the compound in ALO. crucibles. Distribution coefficients of the spectroscopically observed impurities in A1Sb were found to be 0.1 and smaller. Resistivity and Halt coefficients have been determined for some single-crystal specimens cut from the zone-melted ingots. Single crystals of A1Sb have been grown by pulling from the melt. These crystals exhibited low resistivities. The mobility for holes in the crystals has been found to range between 300 and 500 cm~/v-sec.Of the nine Group III-V semiconducting intermetallic compounds, AISb, GaAs, and InP are of major interest for use in the fabrication of solidstate rectifiers and transistors. A considerable amount of work has been done recently on the purification and growth of single crystals and on the study of the electrical properties of the compounds (1). In this paper, the preparation of A1Sb by zone melting and the growth of AISb crystals by crystal pulling are described.

Direct microscopic observation of the movement of growth steps during chemical vapor deposition of epitaxial layers of germanium on germanium substrates, in an open tube reactor, has been employed to study growth mechanisms operative in this system. The reaction studied was the disproportionation of germanium diiodide: 2GeI2false(normalgfalse)=normalGefalse(normalsfalse)+GeI4false(normalgfalse) . Rate of step movement has been measured as a function of step height, substrate temperature, iodide pressure, gas flow rate, and other growth variables. In addition, transpiration measurements have been made to determine the actual partial pressures for gaseous species produced at various sites in the open‐tube flow system. The predominant stepped growth features observed on (111) planes were triangular pyramids. They are shown to be quite minor deviations from the (111) plane, the slope of the side for a typical pyramid being at most 1 in 30. A maximum in rate of step movement has been found with the germanium seed near 360°C, and observable step movement was detected in a narrow temperature range about this optimum temperature. From the observed influence of step height and iodide pressure on rate of step movement it is suggested that growth depends on processes occurring directly at step sites. At high iodide pressure two‐dimensional nucleation of germanium on terrace portions may occur, resulting in an increased concentration of crystalline defects.