Resistivity control in unintentionally doped GaN films grown by MOCVD

The relationship of GaN resistivity to film microstructure and impurity compensation are investigated using transmission electron microscopy, secondary ion mass spectroscopy, X-ray diffraction, and resistance measurements. Unintentionally doped GaN films grown by MOCVD at varying pressures exhibit increased grain size, reduced carbon and oxygen impurity incorporation, reduction in the density of threading dislocations (TDs) with an edge component, and reduced resistivity with increasing growth pressure. Variation in resistivity over eight orders of magnitude is observed as a result of varying the MOCVD growth pressure in a controlled experiment. Our results suggest that disclocations play an important role in the resistivity of GaN. Evidence is presented of impurities segregating at TDs having an edge component, and acting as compensating centers. The control of such compensation as a function of MOCVD growth conditions is outlined. Published by Elsevier B.V.