Effect of Substrate Surface Atom Constitution and The Migration Characteristics of Reactive Atoms on Crystal Structure of Mg_xZn_1–xO Thin Films Deposited by PLD Method

Abstract

Mg x Zn 1−x O thin films were deposited on fused quartz substrate by PLD method with Mg 0.4 Zn 0.6 O source target, and the effect of the substrate surface atom constitution and the migration characteristics of reactive atoms on crystal structure of the MgZnO thin films were studied. Under oxygen-deficient condition, Mg x Zn 1−x O thin film deposited mainly along (200) orientation of cubic structure lattice at temperature below 350 °C because of the alternatively constituted substrate surface by Si and O atoms and the weak horizontal migration of reactive atoms, mix-constituted substrate surface(Si/O areas and O-rich areas) and the intense horizontal migration of reactive atoms introduced phase separation in Mg x Zn 1−x O thin films deposited at higher temperature. Single cubic structure (200) Mg 0.38 Zn 0.62 O thin films was made at 300 °C with Zn composition over theoretical limit in bulk materials, the band gap of which reached 4.2 eV and the MgZnO thin film could detect 330 nm near-UV light. And the available UV range of the cubic Mg x Zn 1−x O thin film deposited at 350 °C was widened to 348 nm near-UV light because of the cubic MgZnO grains with even higher Mg composition in this sample. Under high temperature and oxygen flow rate condition, Mg x Zn 1−x O thin film deposited mainly along the (200) orientation of cubic structure lattice at 2 Pa pressure, Mg x Zn 1−x O thin film deposited mainly along the (111) orientation of cubic structure lattice on O-rich substrate surface when the migration energy of reactive atoms is extremely small at 10 Pa oxygen pressure, and both mixconstituted substrate surface and medium migration energy of reactive atoms cause the phase separation occurred in Mg x Zn 1−x O thin films deposited under medium oxygen pressure. On the basis of the different substrate surface atom constitution and different migration characteristics of reactive atoms considering particular deposition method and condition, some previous results on the formation of different structure Mg x Zn 1−x O thin films and phase separation could also be interpreted. So the available UV range of cubic MgZnO thin film could be adjusted widely from near-UV (348 nm) to vacuum UV (<200 nm) range when both substrate surface atom constitution and migration characteristics of reactive atoms are suitable under given condition by multiple methods.

Ultraviolet photodetectors based on wide bandgap oxide semiconductor films

“…After this study, some scientists began to focus on the mixed-phase ZnMgO UV photodetector. Han et al [73][74][75] fabricated MSM structure UV detectors based on mixed-phase ZnMgO thin films by pulsed laser deposition (PLD) method, and the effect of the substrate surface atom constitution and the migration characteristics of reactive atoms on crystal structure of the ZnMgO thin films have been investigated. [72] In addition, several other methods have been used to improve the performance of ZnO-based UV photodetectors.…”

Blocking Si‐Induced Visible Photoresponse in n‐MgxZn1–xO/p‐Si Heterojunction UV Photodetectors Using MgO Barrier Layer

“…However, due to the low‐energy bandgap of Si, the n ‐Mg x Zn 1– x O/p‐Si devices are sensitive to visible light, and as a consequence, not quite suitable for visible blind UV photodetection applications such as combustion flame monitoring, pollution analysis, missile plume detection, chemical sensing, and intersatellite communications. [ 12–14 ] Recently, it has been reported in the literature that the insertion of a thin layer of SiO 2 or BeO between the Mg x Zn 1– x O film and Si substrate is effective in suppressing the visible photoresponse in Mg x Zn 1– x O/p‐Si devices by blocking the drift of photo‐excited minority carrier from p‐Si to n‐Mg x Zn 1– x O due to high conduction band offset at the p‐Si/insulator interface. [ 15,16 ]…”

Great Enhancement Effect of 20–40 nm Ag NPs on Solar-Blind UV Response of the Mixed-Phase MgZnO Detector

“…The study on wide band gap semiconductor (WBSC) materials (AlGaN, diamond, SiC, Ga 2 O 3 , MgZnO, etc.) that are used in UV photodetectors has emerged during past 20 years. − Compared with other materials, ternary alloy MgZnO materials with different Mg compositions could detect UV light in a wider range from 220 to 380 nm, , and the UV response of MgZnO-based detectors are relative higher at both near UV and solar-blind UV light. , Recently, mixed-phase MgZnO-based UV detector have shown a high response and a small dark current at both near and deep UV light, ,− so the mixed-phase MgZnO thin film is an ideal material for high-performance UV detectors at both solar-blind UV (220–280 nm) and visible-blind UV (300 nm–380 nm) light.…”