GaN is a very important semiconductor with a wide direct bandgap (3.39 eV)

and has strong light emission in blue and UV regions. It has found extensive commercial applications in lasers and light-emitting diodes. Recently Si substrate is regarded as one of most promising substrates for GaN epitaxial growth due to its high quality

low cost

extensively existing in electronic industry and so on. However

it is very difficult to grow high quality GaN epitaxial layer due to great difference in lattice constant and thermal expansion coefficient.In our experiment

GaN film composed of crystalline microsheets was synthesized on Si(111) substrate by chemical vapor deposition

employing Ga

2

O

3

and NH

3

as Ga and N sources respectively. No buffer layer was used. The as-grown product was tested and characterized using SEM

EDS

XRD

TEM and PL. The results show that the as-grown product is a high quality GaN film which is composed of crystalline microsheets with less defects. The size of crystalline microsheets is hundreds of nanometers and the thickness in the range of tens of nanometers. GaN film integrates tightly with Si substrate

the surface of which is flat

compact and no cracks. A strong band-edge emission peak at 367 nm(3.378 eV) is observed. The growth mechanism is discussed briefly.