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Solid Solutions of Grimm–Sommerfeld Analogous Nitride Semiconductors II‐IV‐N 2 (II=Mg, Mn, Zn; IV=Si, Ge): Ammonothermal Synthesis and DFT Calculations
Author(s) -
Mallmann Mathias,
Niklaus Robin,
Rackl Tobias,
Benz Maximilian,
Chau Thanh G.,
Johrendt Dirk,
Minár Ján,
Schnick Wolfgang
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201903897
Subject(s) - wurtzite crystal structure , band gap , nitride , solid solution , materials science , semiconductor , direct and indirect band gaps , electronic structure , chemistry , solubility , spectroscopy , crystallography , analytical chemistry (journal) , computational chemistry , zinc , nanotechnology , metallurgy , organic chemistry , physics , optoelectronics , layer (electronics) , quantum mechanics
Grimm–Sommerfeld analogous II‐IV‐N 2 nitrides such as ZnSiN 2 , ZnGeN 2 , and MgGeN 2 are promising semiconductor materials for substitution of commonly used (Al,Ga,In)N. Herein, the ammonothermal synthesis of solid solutions of II‐IV‐N 2 compounds (II=Mg, Mn, Zn; IV=Si, Ge) having the general formula (II a 1− x II b x )‐IV‐N 2 with x ≈0.5 and ab initio DFT calculations of their electronic and optical properties are presented. The ammonothermal reactions were conducted in custom‐built, high‐temperature, high‐pressure autoclaves by using the corresponding elements as starting materials. NaNH 2 and KNH 2 act as ammonobasic mineralizers that increase the solubility of the reactants in supercritical ammonia. Temperatures between 870 and 1070 K and pressures up to 200 MPa were chosen as reaction conditions. All solid solutions crystallize in wurtzite‐type superstructures with space group Pna 2 1 (no. 33), confirmed by powder XRD. The chemical compositions were analyzed by energy‐dispersive X‐ray spectroscopy. Diffuse reflectance spectroscopy was used for estimation of optical bandgaps of all compounds, which ranged from 2.6 to 3.5 eV (Ge compounds) and from 3.6 to 4.4 eV (Si compounds), and thus demonstrated bandgap tunability between the respective boundary phases. Experimental findings were corroborated by DFT calculations of the electronic structure of pseudorelaxed mixed‐occupancy structures by using the KKR+CPA approach.