The role of threading dislocations in the physical properties of GaN and its alloys

In this paper, we review progress on understanding the role of threading dislocations (TDs) in the physical properties of GaN and its alloys. A growing body of work provides compelling evidence that TDs in the group-III nitrides behave as non-radiative recombination centers, have energy levels in the otherwise forbidden energy gap, act as charged scattering centers in doped materials, and provide a leakage current pathway. In comparison with conventional III-V semiconductors, the relatively small minority carrier diffusion length L-d ( similar to 50 nm) in the III-nitrides, combined with favorable TD geometries, minimize dislocation-related degradation. The small value of L-d also allows for appreciable optical emission in materials with TD densities as high as 10(10) cm(-2). (C) 1999 Elsevier Science B.V. All rights reserved.