Fig. 1. (Color online) RBS random and channeling spectra of (a), (b) as-sputtered and (c), (d) post-annealed AlN along (a), (c) [0001] and (b), (d) [12¯13] directions; (e) angular scan in the AlN (101¯0) plane at different depths, and the normalized channeling signals along [0001] and [12¯13] directions are zoomed in (f) and (g), respectively; (h) the χ_min values of as-sputtered and post-annealed AlN along [0001] and [12¯13] directions as a function of depth.

Fig. 2. (Color online) (a) X-ray rocking curves (XRCs) of AlN-(002) and -(102) crystalline planes after annealing; (b) optical photograph of 6-inch single crystalline AlN template; (c) FWHM values of XRC-(002) and -(102) crystalline planes at positions marked in (b); (d) XRCs of (002) and (102) crystalline planes of GaN epitaxially grown on 6-inch single crystalline AlN template; (e) bow curves of 6 inch single-crystalline AlN template and HEMT device wafers; (f) atomic force microscopy (AFM) image of HEMT epilayer on single crystalline AlN template.

Fig. 3. (Color online) (a) SEM photograph and (b) cross-sectional diagram of enhancement-mode HEMT device on single-crystalline AlN template.

Fig. 4. (Color online) (a) and (b) Transfer, output characteristics and (c) I_D−V_DS curves of the enhancement-mode p-GaN gate HEMTs on single crystalline AlN template with L_GD of 16 μm after various OFF-state stress. (d) OFF-state breakdown characteristics of the enhancement-mode p-GaN gate HEMTs with L_GD from 10 to 22 µm.