| UV detection technology has become another hot photoelectric detection technology after laser and infrared detection technology in recent years.Due to the strong scattering characteristics of electromagnetic waves in the ultraviolet band in the atmosphere,making the application of ultraviolet detection technology in the military also has great prospects for development and has received widespread attention from researchers.Only the deep ultraviolet light in the 200-280 nm band can not reach the earth’s surface due to the absorption of the ozone layer in the atmosphere,and the light in this band is also known as the solar-blind zone.Gallium oxide,as a third generation semiconductor material,has an ultra-wide forbidden band width and the absorption wavelength just corresponds to the solar-blind region,so it is a natural material for solarblind detection,and the breakdown field strength of gallium oxide is as high as 8 MV/cm,which is suitable for high voltage resistant electronic devices.At present,the development of solar-blind detection technology is mainly divided into external photoelectric effect devices,mainly photomultiplier tubes,and internal photoelectric effect devices,mainly photoconductive diodes,Schottky barrier diodes and heterojunctions.Among them,the photomultiplier tube detection sensitivity is higher,occupying an important position in the market.However,the disadvantages of large size,fragility and high operating voltage restrict its development in many fields.In contrast,Ga2O3-based day-blind UV detector devices have entered people’s vision in recent years due to their small size,low operating voltage and easy integration.In this project,we have studied the controllable preparation of heterojunction epitaxial films,the energy band regulation of heterojunction interface and the performance study of solarblind detectors from Ga2O3-based day-blind photodetectors,including the following aspects:(1)For the difficult realization of Ga2O3 p-type doping,Ga2O3based heterojunctions need to find a lattice matching p-type material to be prepared into heterostructures by epitaxial growth.We selected La0.8Ca0.2MnO3(LCMO)as the p-type material and systematically studied the optimal growth conditions for depositing β-Ga2O3 and LCMO singlecrystal films on strontium titanate substrates,which laid the foundation for the preparation of day-blind photodetectors.(2)Study the energy band alignment at the interface of βGa2O3/LCMO heterostructures.In order to achieve better performance of the day-blind photodetector,we tested the heterojunction by X-ray photoelectron spectroscopy and obtained a valence band offset of 2.55 eV at the contact interface,which is conducive to the occurrence of avalanche breakdown effect,and a large valence band shift can effectively block the injection of holes,lengthen the acceleration distance of carriers and facilitate the occurrence of collisional ionization in the lattice.(3)The performance of the β-Ga2O3/LCMO pn junction day-blind photodetector(APD)was tested and calculated.Through the semiconductor testbed we conducted electrical tests on the APD such as IV and spectral response,and obtained a series of key performance indexes of the APD such as multiplicative gain,responsivity,detectivity,external quantum efficiency,dynamic linear range,and noise equivalent power.Among them,the β-Ga2O3/LCMO pn junction APD achieves an ultra-high multiplicative gain of up to 3 ×105. |
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