Memory Effect and Redistribution of Mg into Sequentially Regrown GaN Layer by Metalorganic Chemical Vapor Deposition

Abstract

Mg redistribution into a subsequently regrown GaN epilayer by metalorganic chemical vapor deposition (MOCVD) is studied. Dopant profiles from secondary ion mass spectrometry (SIMS) on n–p–n GaN samples have been analyzed. The regrowth study in a Mg-free reactor reveals that a Mg-rich film is present on MOCVD as-grown GaN:Mg base layers and can be removed by an acid etch, and that a slow Mg decay into the sequentially regrown GaN results from this Mg-rich surface film. We believe the commonly seen Mg memory effect in MOCVD causes the accumulation of Mg on the surface. From a MOCVD regrowth on n–p–n GaN grown by molecular beam epitaxy (MBE), the Mg diffusion constant is calculated to be about 3 ×10^-15 cm²/s at 1160°C for Mg concentrations between 5 ×10¹⁷ cm^-3 and 1 ×10¹⁹ cm^-3. The roles of memory effect, surface segregation, and diffusion associated with Mg are addressed.