Nanoscale Electrostructural Characterization of Compositionally Graded AlxGa1-xN Heterostructures on GaN/Sapphire (0001) Substrate

作者：Kuchuk Andrian V^*; Lytvyn Petro M; Li Chen; Stanchu Hryhorii V; Mazur Yuriy I; Ware Morgan E; Benamara Mourad; Ratajczak Renata; Dorogan Vitaliy; Kladko Vasyl P; Belyaey Alexander E; Salamo Gregory G

来源：ACS Applied Materials & Interfaces, 2015, 7(41): 23320-23327.

DOI：10.1021/acsami.5b07924

• AlxGa1-xN
• graded layers
• polarization doping
• step-bunching effect
• threading dislocations
• charge accumulation

We report on AlxGa1-xN heterostructures resulting from the coherent growth of a positive then a negative gradient of the Al concentration on a [0001]-oriented GaN substrate. These polarization-doped p-n junction structures were characterized at the nanoscale by a combination of averaging as well as depth-resolved experimental techniques including: cross-sectional transmission electron microscopy, high-resolution X-ray diffraction, Rutherford backscattering spectrometry, and scanning probe microscopy. We observed that a small miscut in the substrate orientation along with the accumulated strain during growth led to a change in the mosaic structure of the AlxGa1-xN film, resulting in the formation of macrosteps on the surface. Moreover, we found a lateral modulation of charge carriers on the surface which were directly correlated with these steps. Finally, using nanoscale probes of the charge density in cross sections of the samples, we have directly measured, semiquantitatively, both n- and p-type polarization doping resulting from the gradient concentration of the AlxGa1-xN layers.

• 出版日期2015-10-21