GaN (Gallium nitride) has been grown successfully on sapphire by RF plasma
MBE through optimizing the growth condition. Two dimensional triple axis ma
pping (TDTAM) was used to characterize the GaN epilayers. The dislocation d
ensity in the epilayers was estimated to be about 7.8 x 10(8) cm(-2) accord
ing to the mosaic model. The 77K photoluminescence (PL) of the Si-doped GaN
with different concentration show that Si can act both donor and acceptor
at very high concentration. Transmission spectrum has also been measured fo
r further understanding of the sample. (C) 2000 Elsevier Science S.A. All r
ights reserved.