Study On The Preparation,Physical Property Control Of Gallium Oxide And Its Optoelectrical Device

The photoelectric coupling characteristics of semiconductor materials and their information functional devices have always been the international frontier and research focus in the field of condensed matter physics.As a typical representative of the third generation semiconductor material,gallium oxide has excellent optical properties,high breakdown electric field（8×10⁶V/cm）,big Baliga’s figure of merit（3444）,and high stability,so it is widely used in solar-blind photodetectors,power devices,gas sensors and so on.β-Ga₂O₃has an ultra-wide band-gap of about 4.9 e V,effectively shielding the interference of solar radiation and artificial light sources,making it very suitable for solar-blind ultraviolet photodetectors.High quality gallium oxide films play a crucial role in the performance of devices.In unintentional doping intrinsicβ-Ga₂O₃films,oxygen vacancies act as donor impurities,making it exhibit n-type conductive behavior,thus preparing stable p-typeβ-Ga₂O₃film is a huge challenge.In addition,with the development of intelligent wearable devices,future optoelectronic devices are required to have the capabilities of flexibility,adaptation,and self driving.In view of this,this thesis takesβ-Ga₂O₃as the research object,and the research is carried out in the aspects of film growth,p-type doping,solar-blind ultraviolet photodetectors and flexible optoelectronic devices.The main research results are as follows:（1）High-quality intrinsicβ-Ga₂O₃films were prepared on c-plane sapphire substrates by pulsed laser deposition technique,by adjusting the growth temperature and oxygen pressure.The crystal quality,stoichiometric ratio,surface morphology and energy band structure of the films can be regulated.The influence of the physical properties of the thin film on the performance of the photodetector was discovered.The effects of growth temperature and oxygen pressure on the films and the corresponding solar-blind photodetectors were explored.It is found that oxygen vacancies inhibit the dark current and response speed of the device,while large grain sizes promote high light response current.Devices based on films grown at 700 ^oC and 20 m Torr have extremely low dark current（0.5 p A）,a large photo to dark current ratio（～2×10⁴）,a big response of 6.2 A/W and an external quantum efficiency of3600%.（2）High-quality p-type Mg-dopedβ-Ga₂O₃films with stable optoelectronic properties and corresponding solar-blind UV photodetectors were successfully prepared.The effects of growth temperature and oxygen pressure on the films and the corresponding solar-blind photodetectors were explored.Devices based on films grown at 750 ^oC and 30 m Torr have extremely low（0.19 p A）and a large photo to dark current ratio（>10⁴）,and their photoelectric performance remains unchanged after being stored in air for four weeks.Further,we fabricated field-effect transistors and the conductivity type of Mg-dopedβ-Ga₂O₃films was confirmed to be p-type.Mg:β-Ga₂O₃/β-Ga₂O₃all Ga₂O₃p-n junctions were fabricated,and the response time is reduced to 10 ms.This work provides the guidance for the preparation of p-typeβ-Ga₂O₃films and corresponding application in ultraviolet photodetection,and also provides a new idea for the design ofβ-Ga₂O₃-based optoelectronic devices.（3）The flexible devices based onβ-Ga₂O₃films were fabricated by a stamp-based transfer technology,and flexible imaging sensors and wearable ultraviolet alarms were realized.Furthermore,aβ-Ga₂O₃/WSe₂van der Waals heterojunction were prepared.The energy band structure of this heterojunction was revealed using a Kelvin probe microscope,and a solar-blind communication system was constructed.β-Ga₂O₃films were prepared on the flexible PET substrate by a stamp-based printing techniques,and the corresponding flexible solar-blind photodetectors have a low dark current of 1.7 p A and a large photo to dark current ratio of 1.2×10³,exhibiting good photoelectric performance and stability at a strain of 0.31%.Furthermore,a flexible imaging sensor array and a wearable ultraviolet alarm were fabricated,demonstrating the practical application ofβ-Ga₂O₃-based flexible photodetectors in the field of sola-blind photodetection.Finally,β-Ga₂O₃/WSe₂van der Waals heterojunctions were prepared,and the response time is reduced to 10 ms.A solar-blind communication system has been built.This work not only provides ideas for the design of flexibleβ-Ga₂O₃-based information function devices,but also promotes the development of new wearable optoelectronic devices.