Wide-band gap oxide alloy: BeZnO

Abstract

A wide-band gap oxide alloy, BeZnO, is proposed and studied in this letter. The BeZnO films were deposited on sapphire substrates by our hybrid beam deposition growth method. The value of the energy band gap of BeZnO can be efficiently engineered to vary from the ZnO band gap ͑3.4 eV͒ to that of BeO ͑10.6 eV͒. BeZnO can be used for fabricating films and heterostructures of ZnO-based electronic and photonic devices and for other applications. Changes in the measured energy band gap and lattice constant values with Be content are described for BeZnO alloys.

Theoretical analysis of the crystal structure, band-gap energy, polarization, and piezoelectric properties of ZnO-BeO solid solutions

“…17,27 This is based on limited θ-2θ X-ray Diffraction (XRD) experiments on epitaxial or highly oriented Zn 1-x Be x O films grown on the (0001) α-Al 2 O 3 substrates. 16,25,31 XRD results show that the out-of-plane lattice parameter of Zn 1-x Be x O films varies linearly with increasing x. 16 However, information regarding other structural or crystallographic properties, such as the relative atomic positions and symmetry in the basal plane, that are needed to completely characterize the crystal structure of these alloys is lacking.…”

“…16,25,31 XRD results show that the out-of-plane lattice parameter of Zn 1-x Be x O films varies linearly with increasing x. 16 However, information regarding other structural or crystallographic properties, such as the relative atomic positions and symmetry in the basal plane, that are needed to completely characterize the crystal structure of these alloys is lacking. Such factors play a significant role on the growth morphology, band structure, spontaneous polarization, and piezoelectric properties of a material.…”

“…14 Band gap engineering of ZnO can be achieved by alloying with MgO (E g =7.70 eV) for UV applications and such alloys can also be used as barrier layers in ZnO/(Zn,Mg)O superlattices for quantum well devices. 15,16 However, phase separation occurs in Zn 1-x Mg x O solid solutions when the Mg composition exceeds 33%. 1,16 This is due to the differences in the crystal structures of ZnO [wurtzite (W), P6 3 mc] and MgO (rocksalt, Fm 3 m).…”

“…15,16 However, phase separation occurs in Zn 1-x Mg x O solid solutions when the Mg composition exceeds 33%. 1,16 This is due to the differences in the crystal structures of ZnO [wurtzite (W), P6 3 mc] and MgO (rocksalt, Fm 3 m). As such, the UV absorption range is limited to 3.37-3.90 eV in the Zn 1-x Mg x O system for x<0.33.…”

“…12,17,18 It was shown that Zn 1-x Be x O thin films can be deposited using hybrid beam deposition 19 with no phase separation over the entire composition range. 16 Furthermore, since in Zn 1-x Be x O the band gap can theoretically be tuned from 3.37 to 10.60 eV, this materials system may replace Zn 1-x Mg x O solid solutions that are being considered in applications such as field effect transistors, polymer-oxide hybrid solar cells, quantum Hall effect devices, high-k films on Si, and acoustic resonators. [20][21][22][23][24] While there have been some efforts to understand, describe, and measure the lattice parameters, the band gap, and optical properties of Zn 1-x Be x O in thin films, 16,17,[25][26][27][28] the potential of this materials system for applications described above has not been fully explored.…”