Reduction of leakage current of p-n junction by using air-bridged lateral epitaxial growth technique

The reverse bias leakage current of p-n junction devices was drastically reduced by decreasing the threading dislocation density with an air-bridged lateral epitaxial growth (ABLEG) technique in comparison with growing directly on a sapphire substrate. In the wing region of ABLEG-GaN, the threading dislocation density is 10(6) cm(-2) and the wing tilt angle is 0.1degrees. The amount of reduction in the reverse bias leakage current was above two orders of magnitude. The reverse bias leakage current of p-n junction devices is well explained by the Poole-Frenkel conduction model. The energy of the Poole-Frenkel trap level was estimated to be 0.49 eV in the devices directly grown on a sapphire substrate, which have large dislocation density. On the other hand, the trap level estimated in devices on ABLEG, which have low dislocation density, was much shallower. From these results, it is thought that such a deeper trap level is related to threading dislocation in growing directly on sapphire. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim