Characterization of AlN/AlGaN/GaN:C heterostructures grown on Si(111) using atom probe tomography, secondary ion mass spectrometry, and vertical current-voltage measurements

Complementary studies of atom probe tomography, secondary ion mass spectrometry, and vertical current-voltage measurements are carried out in order to unravel the influence of C-doping of GaN on the vertical leakage current of AlN/AlGaN/GaN:C heterostructures. A systematic increment of the vertical blocking voltage at a given current density is observed in the structures, when moving from the nominally undoped conditions—corresponding to a residual C-background of ∼10¹⁷cm⁻³—to a C-content of ∼10¹⁹cm⁻³ in the GaN layer. The value of the vertical blocking voltage saturates for C concentrations higher than ∼10¹⁹cm⁻³. Atom probe tomography confirms the homogeneity of the GaN:C layers, demonstrating that there is no clustering at C-concentrations as high as 10²⁰cm⁻³. It is inferred that the vertical blocking voltage saturation is not likely to be related to C-clustering.