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Structures and Polarity of III‐Nitrides: Phase Diagram Calculations Using Absolute Surface and Interface Energies
Author(s) -
Akiyama Toru,
Nakane Harunobu,
Uchino Motoshi,
Nakamura Kohji,
Ito Tomonori
Publication year - 2018
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201700329
Subject(s) - polar , nitride , phase diagram , materials science , polarity (international relations) , substrate (aquarium) , phase (matter) , crystallography , condensed matter physics , chemistry , nanotechnology , layer (electronics) , physics , biochemistry , oceanography , organic chemistry , astronomy , geology , cell
The structures and polarity of group‐III nitride semiconductors are theoretically investigated by calculating individual energy of polar surfaces and interfaces using density functional calculations. Using the surface and interface energies, we demonstrate phase diagrams as functions of temperature and pressure for polar AlN on 6H‐SiC(0001) substrate as well as polarity inversion of GaN on N‐polar AlN ( 000 1 ¯ ) substrate. The calculated phase diagram for AlN on Si‐face SiC under H‐rich conditions reveals that the H‐terminated Al‐polar surfaces with substitutional Al atoms at AlN/SiC interface are stabilized over the wide range of Al pressure below 1320 K while that with N adatom are favorable for temperature beyond 1320 K. In contrast, the calculated phase diagram for GaN on N‐polar AlN ( 000 1 ¯ ) substrate clarifies that the H‐terminated Ga‐polar surface with on N‐polar substrate with two monolayers of Al olverlayers is favorable over entire growth conditions. These results suggest that the stability of interface between III‐nitride and substrate rather than surface stability is crucial for the polarity of III‐nitrides.