Query: Fabrication of β-Ga2O3 thin films and solar-blind photodetectors by laser MBE technology

Candidate papers:

abstract: Laser molecular beam epitaxy technology has been employed to deposit b gallium oxide (b Ga2O3) on (0001) sapphire substrates. After optimizing the growth parameters, (2 01) oriented b Ga2O3 thin film was obtained. Ultraviolet visible absorption spectrum demonstrates that the prepared b Ga2O3 thin film shows excellent solar blind ultraviolet (UV) characteristic with a band gap of 5.02 eV. A prototype photodetector device with a metal semiconductor metal structure has been fabricated using high quality b Ga2O3 film. The device exhibits obvious photoresponse under 254 nm UV light irradiation, suggesting a potential application in solar blind photodetectors.
author_names: Daoyou Guo

Zhenping Wu

Peigang Li

Yue Hua An

Han Yang Liu

Xuncai Guo

Hui Yan

Guofeng Wang

Changlong Sun

Linghong Li

Weihua Tang
title: Fabrication of b Ga_2O_3 thin films and solar blind photodetectors by laser MBE technology
year: 2014

abstract: Abstract Herein, we are reporting the fabrication of high performance solar blind photodetectors using b Ga2O3 thin films of varying thicknesses grown on single crystal (0001) Sapphire substrate by pulsed laser deposition (PLD) technique. Thickness of the b Ga2O3 films was varied by varying the number of ablating laser shots from 1000 to 15,000 (1 k to 15 k) The effect of thickness on the structure, surface morphology and optical properties of the films was investigated using several state of the art techniques such as X ray diffraction (XRD) Raman spectroscopy, scanning electron microscopy (SEM) atomic force microscopy (AFM) and ultraviolet visible (UV Vis) spectroscopy. All the films were found to be made of phase pure b Ga2O3 with high crystal quality. The orientation of the films was found to gradually change from 201) to 201)(400) as the number of laser shots increased from 1 k to 15 k. The bandgap of the films made with 1 k laser shots was found to be 5.26 eV which decreased monotonously with increase in number of laser shots and became 4.79 eV for the films made with 15 k laser shots. The detailed time resolved photoresponse measurements showed that the films made with 2 k shots exhibit the best photoresponse characteristic among all the films with a high Iphoto/Idark ratio of ~6.7 x 104 and short rise (0.38 ms) and decay times (142 ms) Our results indicate that the PLD grown b Ga2O3 thin films, with optimized thickness, can play a major role in next generation solar blind ultraviolet photodetector technology.
author_names: Hao Shen

Karthikeyan Baskaran

Yinong Yin

Kun V Tian

Libing Duan

Xiaoru Zhao

Ashutosh Tiwari
title: Effect of thickness on the performance of solar blind photodetectors fabricated using PLD grown b Ga2O3 thin films
year: 2020

abstract: Ga2 xSnxO3 thin films were deposited on c plane Al2O3 (0001) substrates with different Sn content by laser molecular beam epitaxy technology (L MBE) The Sn content x was varied from 0 to 1.0. \bar{2}01$$2 01) oriented b phase Ga2 xSnxO3 thin films were obtained at the substrate temperature of 850degC in the vacuum pressure of 5 x 10 5 Pa. The crystal lattice expanded and the energy band gap decreased with the increase of Sn content for Sn4+ ions incorporated into the Ga site. The n type conductivity was generated effectively through doping Sn4+ ions in the Ga2O3 lattice in the oxygen poor conditions. The solar blind (SB) photodetectors (PDs) based on Ga2 xSnxO3 (x 0, 0.2) thin films were fabricated. The current intensity and responsivity almost increased by one order of magnitude and the relaxation time constants became shorter for x 0.2. Our work suggests that the performance of PD can be improved by doping Sn4+ ions in Ga2O3 thin films.
author_names: Xiaolong Zhao

Wei Cui

Zhenping Wu

Daoyou Guo

Peigang Li

Yue Hua An

Linghong Li

Weihua Tang
title: Growth and Characterization of Sn Doped b Ga2O3 Thin Films and Enhanced Performance in a Solar Blind Photodetector
venue: Journal of Electronic Materials
year: 2017

abstract: Monoclinic gallium oxide thin films were deposited on c plane sapphire substrates at various substrate temperatures ranging from 450 degC to 700 degC by radio frequency magnetron sputtering technology. X ray diffraction results showed that the deposited b Ga2O3 films were oriented at 2 01) direction. As the substrate temperature increased, the intensity of b Ga2O3 peaks increased and bandgap decreased accordingly. Metal/semiconductor/metal structured solar blind photodetectors based on b Ga2O3 thin films growing at various substrate temperatures had been fabricated. The growth temperatures of thin films had no obvious influence on dark current and response to 365 nm light illuminations. The photoelectric properties such as responsivity and response speed of the thin films to 254 nm light illuminations were growth temperature dependent. At an applied bias of 50 V, the photodetectors prepared with 450 degC grown film had the highest responsivity of 2.18 A/W, and the photodetectors prepared with 700 degC grown film had the shortest rising time of 0.95 s under 254 nm light illuminations.
author_names: Wei Cui

Qinghua Ren

Yusong Zhi

X L Zhao

Z P Wu

P G Li

W H Tang
title: Optimization of Growth Temperature of b Ga2O3 Thin Films for Solar Blind Photodetectors.
venue: Journal of nanoscience and nanotechnology
year: 2018

abstract: Abstract In this study, Sn doped b Ga2O3 thin films were successfully grown by selecting stable, solid and nontoxic mixed powders (SnO2, Ga2O3 and graphite) as precursors during chemical vapor deposition in a cheap and traditional tube furnace reactor. By doping more Sn, optical bandgap of the films obviously shifted from ~5.7 eV to ~5.2 eV. At 50 V, the dark current of metal semiconductor metal solar blind ultraviolet (UV) photodetectors increased from 0.04 pA to 2.57 pA as more Sn was doped, along with the improved responsivity from 0.2 mA/W to 80 mA/W and reduced decay time from 0.207 s to 22 ms, which may be ascribed to much faster transit time from lower boundary barrier in a grain boundary related transport process. In comparison with the devices on Sn doped Ga2O3 thin films by expensive MBE, our photodetectors with comparable responsivity show advantages of much lower dark current and faster decay time, which may provide a cheap and easy way to investigate their application for solar blind UV photodetectors.
author_names: Ying-jie Lu

Kang Xu

Yan Cui

Ling Cao

Xiuyan Li
title: Growth and characterization of Sn doped b Ga2O3 thin films by chemical vapor deposition using solid powder precursors toward solar blind ultraviolet photodetection
year: 2020

abstract: Abstract High quality 201) oriented b Ga2O3 thin films were epitaxially grown on c sapphire substrates by pulsed laser deposition (PLD) at various substrate temperatures using a b Ga2O3 ceramic target. These films were then used to fabricate metal semiconductor metal (MSM) solar blind photodetectors (PDs) based on an Au/b Ga2O3/Au structure. The crystal quality, atomic ratio of O/Ga, and bandgap of the b Ga2O3 films all increased with increasing growth temperature, causing the dark current and response time of the PDs to decrease dramatically. The PD based on the b Ga2O3 film grown at 700 degC exhibited the best performance, with a low dark current of 10.6 pA at 10 V and a high peak responsivity of 18.23 A/W (at 255 nm) Furthermore, the response time of the fabricated PD was fast (trise: 0.062/0.379 s, tdeacy: 0.058/0.663 s) These results represent the state of art performance in dark current for PLD grown b Ga2O3 based MSM solar blind detectors.
author_names: Qile Wang

Jian Jhih Chen

Mingkai Li

Yinmei Lu

Kevin Homewood

Gang Chang

Hong Chen

Yunbin He
title: Influence of growth temperature on the characteristics of b Ga2O3 epitaxial films and related solar blind photodetectors
venue: Applied Surface Science
year: 2019

abstract: Highly oriented Ga2 x Zn x O3 thin films with different doping concentrations were grown on (0 0 0 1) sapphire substrates by laser molecular beam epitaxy technology. The expansion of lattice and the shrinkage of band gap with increasing doping level confirms the chemical substitution of Zn2+ ions into the Ga2O3 crystal lattice. The emission intensity of blue violet emission bands enhanced with the increase of (ZnGa) under 254 nm ultraviolet excitation, and the maximum was obtained at x 0.8. A metal semiconductor metal structured solar blind photodetector based on Ga2 x Zn x O3 (x 0, 0.8) was made, the increasing responsivity and diminishing relaxation time constants for b Ga2 x Zn x O3 (x 0.8) photodetector were observed with 254 nm ultraviolet illumination.
author_names: Xiaolong Zhao

Zhenping Wu

Yusong Zhi

Yue Hua An

Wei Cui

Linghong Li

Weihua Tang
title: Improvement for the performance of solar blind photodetector based on b Ga2O3 thin films by doping Zn
year: 2017

abstract: Abstract Solar blind UV detectors based on gallium oxide thin films have attracted extensive attention for potential civil and military applications. Substrate selection plays an important role for hetero epitaxial growth of gallium oxide thin films. Herein, b Ga2O3 thin films were deposited on r plane and c plane sapphire substrates by plasma assisted molecular beam epitaxy. The microstructure of the b Ga2O3 thin films were analyzed by X ray diffraction and transmission electron microscope. 2 01 oriented b Ga2O3 thin films were grown on c plane sapphire. While, b Ga2O3 thin films with both (100) and (001) oriented grains were prepared on r plane sapphire. Moreover, photodetectors were fabricated. Detectivity of the photodetectors made from b Ga2O3 thin films on r plane and c plane sapphire is about 1.3 x 1014 Jones and 7.2 x 1013 Jones, respectively. The b Ga2O3 thin films grown on r plane sapphire is benefit for solar blind UV detectors fabrication.
author_names: Xingzhao Liu

Qing Liu

Bowen Zhao

Yixuan Ren

Bowan Tao

Wanli Zhang
title: Comparison of b Ga2O3 thin films grown on r plane and c plane sapphire substrates
year: 2020

abstract: A thin film type b Ga2O3/ZnO heterojunction was constructed for the first time by radio frequency magnetron sputtering of a b Ga2O3 layer on a (0001) ZnO single crystalline substrate. The heterojunction presents a typical positive rectification in the dark, and shows a solar blind deep ultraviolet photoelectric characteristic. Under zero bias, the photodetector based on a b Ga2O3/ZnO heterojunction exhibits an I photo/I dark ratio of ~14.8 under a 254 nm light illumination with a light intensity of 50 mW cm 2, showing a characteristic of working with zero power consumption. The photocurrent linear increases and the response time decreases with the increase of the light intensity. The photodetector shows a R l of 0.35 A W 1 and an EQE of 1.7 x 102% under 254 nm illumination of 50 mW cm 2 and a negative bias of 5 V. This study presents a promising candidate for use in solar blind deep ultraviolet photodetection.
author_names: Daoyou Guo

H Z Shi

Y P Qian

M J Lv

Peigang Li

Y Su

Q Liu

Keke Chen

Shunli Wang

Can Cui

Changqing Li

Weihua Tang
title: Fabrication of b Ga2O3/ZnO heterojunction for solar blind deep ultraviolet photodetection
year: 2017

abstract: Abstract In this manuscript, an ultralow dark current solar blind photodetector based on b Ga2O3/4H SiC heterojunction is generated by depositing b Ga2O3 thin film on n type 4H SiC substrates using Pulse Laser Deposition method. It is found that the excellent performances of our device with ultralow dark current (0.167 nA) as well as high Iphoto/Idark ration (384.3) are obtained with thermal annealing at optimized temperature, which is due to the improvement of interface defects in the b Ga2O3/4H SiC heterojunction through high temperature annealing. Moreover, the detectivity and linear dynamic range of the device are high as 8.23 x 1011 Jones and 51.70 dB, respectively, along with faster response speed (a rise time of 0.18 s and a decay time of 0.31s) which are attributed to the co effect of reducing in defects at the interface of heterojunction and the existence of appropriate amount of mixed crystal orientation in b Ga2O3 films with the optimizing the annealing temperature. The electronic transport mechanism in the b Ga2O3/4H SiC heterojunction photodetector is proposed in details with the energy band diagram.
author_names: Jiangang Yu

Zizhuo Nie

Linpeng Dong

Lei Yuan

Dejun Li

Yu Huang

Lichun Zhang

Yuming Zhang

Renxu Jia
title: Influence of annealing temperature on structure and photoelectrical performance of b Ga2O3/4H SiC heterojunction photodetectors
venue: Journal of Alloys and Compounds
year: 2019