A new method of reducing dislocation density in GaN layer grown on sapphire substrate by MOVPE

A method to drastically reduce dislocation density in a GaN film grown on s apphire substrate is newly developed. In this method, a very thin SixN1-x w as deposited on the sapphire substrate at low temperature before growing co nventional low-temperature GaN buffer layer. By transmission electron micro scope (TEM), the density of threading dislocation originating from the inte rface between a sapphire substrate and GaN layer decreases to be almost inv isible in the observed area from 7 x 10(8/)cm(2) in the conventional method . Atomic force microscopy of a deposited thin SiN indicates that there exis ts nanometer-sized holes in a thin SiN layer, which probably enhance latera l growth and then decrease the dislocation density. The electrical properti es were investigated with respect to the SiN deposition time. With the incr ease of SiN deposition time up to 125 s, the mobility increases and the car rier density decreases. However. if the SiN deposition time is further incr eased, the mobility decreases and the carrier density increases. (C) 2000 E lsevier Science B.V. All rights reserved.