Semiconducting. single crystal wurtzite GaN nanowires have been grown by di
rect reaction of metal Ga with NH3 in a tube furnace. This paper discusses
the growth mechanism. Nanowires grow only between 825 degreesC and 925 degr
eesC. Their diameters vary between 20 and 150 nm and depend directly on tem
perature and NH3 flow rate. Wires as long as 500 mum have been fabricated;
once wires have formed, their length increases directly with time in the re
actor. There are three different stages in the process, each of which has i
ts own mechanism, First. a nearly amorphous GaN matrix forms, followed by g
rowth of hillocks of thin GaN platelets. Finally, nanowires emerge from the
edges of the platelets in characteristic directions, This analysis can be
used as a guide for controlling GaN wire diameters and lengths. Strategies
for growth of thinner and thicker nanowires are suggested. Thicker cylindri
cal structures denoted as rods grow from the face of the platelets. Descrip
tion of their growth mechanism requires further study. (C) 2001 Elsevier Sc
ience BN. All rights reserved.