Metalorganic chemical vapor deposition of GaN on Si(111): Stress control and application to field-effect transistors

Two schemes of nucleation and growth of gallium nitride on Si(111) substrat es are investigated and the structural and electrical properties of the res ulting films are reported. Gallium nitride films grown using a 10-500 nm-th ick AlN buffer layer deposited at high temperature (similar to 1050 degrees C) are found to be under 260-530 MPa of tensile stress and exhibit cracking , the origin of which is discussed. The threading dislocation density in th ese films increases with increasing AlN thickness, covering a range of 1.1 to >5.8 x 10(9) cm(-2). Films grown using a thick, AlN-to-GaN graded buffer layer are found to be under compressive stress and are completely crack fr ee. Heterojunction field effect transistors fabricated on such films result in well-defined saturation and pinch-off behavior with a saturated current of similar to 525 mA/mm and a transconductance of similar to 100 mS/mm in dc operation. (C) 2001 American Institute of Physics.