Fig. 4: Electrical properties of MiGs on n-type and p-type GaN.
From: Observation of 2D-magnesium-intercalated gallium nitride superlattices
a, The capacitance–voltage characteristics (1/C²–V plot) of a lightly n-doped (0001) GaN epilayer on an n-GaN substrate, annealed with Mg at varying temperatures, are compared with those of a blank sample. Frequency, 100 kHz; a.c. level, 20 mV. b, Bulk dopant concentration as a function of depth from the surface, extracted from the 1/C²–V plot (error bands, s.d.; n = 5). Inset, the varying depletion-region depths in lightly n-doped (0001) GaN, annealed with Mg at varying temperatures, compared with the blank sample (error bars, s.d., n = 5). c, STEM images with progressively magnified views demonstrate that an initial p-type GaN epilayer, annealed with Mg at 500 °C for 10 min, exhibits a rough surface but without signs of Mg intercalation. Scale bars: 200 nm (left), 20 nm (middle), 5 nm (right). d, STEM images with progressively magnified views indicate that the p-type GaN epilayer on u-GaN (unintentionally doped, semi-insulating GaN)/n-GaN substrate, annealed with Mg at 550 °C for 10 min, exhibits a rough surface with Mg intercalation characteristic of the early-stage formation of a MiGs structure (arrow). Scale bars: 200 nm (upper left), 20 nm (upper right), 20 nm (lower left), 5 nm (lower right). e, Current–voltage (I–V) characteristics of the transfer-length-method test structure fabricated on the p-type GaN samples, annealed with a selective-area-patterned metallic Mg film at 500 °C (10 min) and 550 °C (10 min) compared with a blank sample.
