Abstract
Cubic GaN has been grown under gallium (Ga)-rich growth conditions using radio frequency nitrogen plasma molecular beam epitaxy on MgO(001) substrates. Reflection high energy electron diffraction patterns indicate the smoothness of the
c
-
Ga
N
surface and show
2
×
and even
8
×
periodicities after the growth at sample temperature
T
s
<
200
°
C
and
1
×
1
at higher temperatures. Scanning tunneling microscopy images reveal a sequence of variant surface reconstructions including
c
(
4
×
12
)
,
4
×
7
,
c
(
4
×
16
)
,
4
×
9
,
c
(
4
×
20
)
, and
4
×
11
. These variant reconstructions correspond to slightly different Ga adatom coverages all less than
1
∕
4
ML, with
4
×
11
having the highest, and
c
(
4
×
12
)
the lowest Ga coverage. The electronic properties of these six variant reconstructions are investigated, and they are found to have a metallic nature.