Epitaxial Zn3n2 Thin Films By Molecular Beam Epitaxy: Structural, Electrical, And Optical Properties

Single-crystalline Zn3N2 thin films have been grown on MgO (100) and YSZ (100) substrates by plasma-assisted molecular beam epitaxy. Depending on growth conditions, the film orientation can be tuned from (100) to (111). For each orientation, x-ray diffraction and reflection high-energy electron diffraction are used to determine the epitaxial relationships and to quantify the structural quality. Using high-temperature x-ray diffraction, the Zn3N2 linear thermal expansion coefficient is measured with an average of (1.5 +/- 0.1) x 10(-5 )K(-1) in the range of 300-700 K. The Zn3N2 films are found to be systematically n-type and degenerate, with carrier concentrations of 10(19)-10(21 )cm(-3) and electron mobilities ranging from 4 to 388 cm(2 )V(-1 )s(-1). Low-temperature Hall effect measurements show that ionized impurity scattering is the main mechanism limiting the mobility. The large carrier densities lead to measured optical bandgaps in the range of 1.05-1.37 eV due to Moss-Burstein band filling, with an extrapolated value of 0.99 eV for actual bandgap energy.