Surface stoichiometry and activity control for atomically smooth low dislocation density ZnO and pseudomorphic MgZnO epitaxy on a Zn-polar ZnO substrate by the helicon-wave-excited-plasma sputtering epitaxy method

Abstract

The helicon-wave-excited-plasma sputtering (HWPS) method was exemplified to be one of the versatile epitaxial growth techniques for the fabrication of low dislocation density semiconductor epilayers and heterostructures exhibiting atomically smooth surface morphology. For a case study, ZnO homoepitaxy and MgxZn1−xO (x=0.08,0.19) heteroepitaxy on a Zn-polar ZnO substrate were carried out. According to the surface damage-free property, high temperature growth with appropriate stoichiometry control enabled the growth of ZnO homoepitaxial layers exhibiting a smooth surface morphology with 0.26 nm high monolayer atomic steps. Their tilt and twist mosaics reflecting the threading dislocation densities having screw and edge components were comparable to those of the substrate, being under the resolution limit (18 arcsec). The surface morphology and crystal mosaicity of pseudomorphic MgxZn1−xO (x≤0.19) epilayers were quite similar to those of the ZnO underlayer. The luminescence spectra of the ZnO and MgxZn1−xO epilayers at 293 K exhibited a predominant near-band-edge emission and negligible broad emission bands due to deep levels. The results indicate that the growth mode of the HWPS method resembles that of molecular beam epitaxy methods.

Interface engineering of high-Mg-content MgZnO/BeO/Si for p-n heterojunction solar-blind ultraviolet photodetectors

“…1͑e͒, implies a typical step-flow growth mode which has been reported in both GaN and Mg 0.19 Zn 0.81 O films grown at relatively high temperature. 16,17 This phenomenon is not usual for high-Mgcontent MgZnO prepared at low temperature, which is presumably attributed to the interfacial layer playing a key role to change the growth dynamics of nucleation and relaxation of strain herein. The high crystal quality is thus naturally achieved meanwhile.…”

Growth of single crystalline films on lattice-mismatched substrates through 3D to 2D mode transition

“…, where E β is the FWHM value of the rocking curve for the (0002) plane, and b E is the length of the Burgers vectors for the edge component = = . ( b 1120/3 0 1083 nm ) E [38][39][40] . The estimated edge-type dislocation densities of the films grown with and without the buffer layer are 6.0 × 10 7 cm −2 and 3.7 × 10 10 cm −2 , respectively.…”

Optical characterization by variable angle spectroscopic ellipsometry of nitrogen-doped Mg Zn1−O thin films prepared by the plasma-assisted reactive evaporation method

“…ZnO has attracted attention as a material for ultraviolet optoelectronic devices because it has a direct wide band gap energy (E g ) of 3.37 eV and exciton binding energy of 60 meV [1]. Wurtzite-type Mg x Zn 1-x O films also have attractive properties for optoelectronic materials to form a heterostructure or multi-quantum-well structure with [2][3][4], pulsed laser deposition (PLD) [5,6], metal organic chemical vapor deposition (MOCVD) [7][8][9] and helicon-wave-excited-plasma sputtering epitaxy [10].…”