Preparation And Research On Transport Characteristics Of Niobicture

As a typical representative of IV-VI semiconductors,lead selenide(PbSe)is a direct bandgap semiconductor.The band gap at room temperature is 0.27 eV,which is often used for infrared detection.PbSe film preparation has always been a hot research direction.In the PbSe film growth study,in order to realize the monolithic integration of the infrared focal plane array and the readout circuit,a lot of work is to explore the PbSe thin film growth technology on the surface of the Si substrate,although some progress has been made,but due to the lattice The difference in the constant is huge,and the quality of the PbSe film is still not high.GaSb and PbSe belong to the same cubic crystal structure,their lattice constants are about 6.1 ?,and the large-size GaSb single crystal technology has matured.The high-quality PbSe film should be grown by using GaSb single crystal as the substrate.Regardless of whether Si is used as the substrate or GaSb is used as the substrate,a problem that must be considered when growing the selenide film is that in the Se-rich environment,the S single crystal and the GaSb single crystal surface will be severely affected with Se.Chemical reactions,therefore,the exploration of a suitable buffer layer material has become an important research task for the growth of PbSe films.As an important member of II-VI semiconductor,CdSe has great value in the field of optoelectronics.Because it is the same selenide material as PbSe,and can be grown by molecular beam epitaxy,this paper chooses CdSe as the buffer layer and uses molecular beam epitaxy.As a technical means,we explored the technical solutions for growing high-quality PbSe thin films on the surface of Si single crystals and GaSb single crystals.To this end,the paper carried out the following work:Firstly,the paper firstly used the molecular beam epitaxy method to grow PbSe thin film on single crystal CdSe substrate,and used high purity PbSe as raw material to generate PbSe molecular beam current using standard molecular beam source furnace to optimize the growth process parameters(PbSe source furnace temperature: A PbSe film was grown at 550 ° C,substrate temperature: 300 ° C.The microstructure and electrical properties of the films grown under optimized conditions were measured and characterized.The characterization results show that the grown PbSe film has a cubic crystal structure and is(100)single orientation.The peak shape of the rocking curve is symmetrical,the full width at half maximum is only 0.2°,and the crystal quality is good.On this basis,the paper also carried out X-ray ? scan analysis on the(111)crystal plane of the grown PbSe film.The characterization results show that 12 diffraction peaks appear at equal intervals in the ? scan spectrum,which indicates: There are three different in-plane orientations in the grown PbSe film,and the three differently oriented grains are at an angle of 30 degrees to each other.According to the high-resolution transmission electron microscopy characterization of the PbSe film section,the crystal structure of the grown film is complete,and the interface between the substrate and the film is clear and steep.In summary,although the CdSe single crystal(0001)plane of the hexagonal wurtzite structure has different crystal symmetry from the PbSe(100)plane,the quality of the grown PbSe film is still high,so CdSe can be used as a buffer layer.It is used to grow high-quality PbSe film on GaSb single crystal substrate,which lays a foundation for the research work of this thesis.To this end,the paper further carried out research work on the growth of CdSe buffer layer films on the surface of Si single crystal and GaSb single crystal substrates,using high purity CdSe as raw material,using standard molecular beam source furnace to generate CdSe molecular beam,using low temperature beam source.The Se molecular beam is generated in the furnace.The influence of growth process parameters is systematically studied.The structure and electrical properties of the grown CdSe film are characterized.The experimental results show that when the temperature of the CdSe source is set to 450 °C and the substrate temperature is set to 300.At °C,the quality of the grown film is higher without opening the Se molecular beam source furnace.The surface morphology analysis of the grown film by scanning electron microscopy also shows that the Se molecular beam is not turned on.The surface of the grown film is also more flat;analysis by ray photoelectron spectroscopy shows that the Cd of the grown film is still +2 valence,which is a CdSe film,even without opening the Se molecular beam.In addition,the paper also tested the electrical properties of the GaSb/CdSe heterojunction.From the IV curve of the diode characteristics of the heterojunction obtained,there is a higher Schottky between the GaSb single crystal substrate and the CdSe film.The barrier can play a certain electrical isolation,which is also very important for the buffer layer.In summary,the experimental results show that CdSe can be used as the buffer layer material for Si and GaSb single crystal substrate and PbSe film.Based on the growth of CdSe buffer film,the PbSe film was further grown,and the microstructure and electrical properties of the grown PbSe film were characterized.The effect of CdSe buffer layer on the photoelectric response of PbSe film was studied.The results show that for the PbSe film grown on the surface of the Si substrate,the CdSe buffer layer improves the photoelectric response of the PbSe film,and its response to 1070 nm infrared light is doubled;but for the GaSb substrate.The introduction of CdSe buffer layer does not have a positive effect on the photoelectric response characteristics of PbSe.On the contrary,the PbSe film directly grown on the surface of GaSb has higher optical responsivity.The main reason should be attributed to: GaSb substrate itself and PbSe With good lattice constant and crystal structure matching,the PbSe film directly grown on the surface of the GaSb substrate has higher crystal quality.Therefore,it can be concluded that when the PbSe film is grown on the surface of the GaSb single crystal substrate,the interface is realized.The effective control of the reaction eliminates the need to introduce a buffer layer,which makes it possible to grow a high quality PbSe epitaxial film using a GaSb single crystal substrate.