The Carrier Behavior Of Semiconductor Under High Pressure

Electrons transform not only from localized states to non-localized states but also from non-associated non-related to strong association under high pressure. Under high pressure, a variety of interactions between atomic electrons intertwined result in many new phenomena and new laws. The investigation for carrier behavior under high pressure can reveal the law of the interaction between atomic electrons that located different atomic orbital. It is important method for testing and developing the condensed matter theory. It is hard to be replaced by other means. Electrical transport related physical parameters under high pressure are not only be as the important scale of the material properties under high pressure state but also as the physical parameters to study the dynamic process under high temperature and high pressure.For in situ high pressure carrier behavior investigation, the key scientific question is to obtain accurate physical parameters change and the quantitative contact. II-VI semiconductor is widely used in electrical, magnetic, and optical studies.They are be made for a variety of devices which are used in many fields. Therefore, studied physical parameters of carrier behavior under electromagnetic environment are not only be used to reveal the physical nature of carrier movement and enrich and develop the existing theory of electrical transport but also be use to detect the II-VI semiconductor a variety of interactions between atomic electrons intertwined.In this thesis, using DAC and integrated microcircuit, in situ Hall effect measurement had been proformed under high pressure. Hall effect of HgX(X=S,Se,Te) has been investigated.HgX(X=S,Se, Te) is a typicalⅡ=Ⅵsemiconductor, its various physical parameters are closely related to the impurity, light, temperature, pressure and other factors. Previous studies focused on change of resistivity with pressure under high pressure. According to the resistivity with temperature determine its electrical properties, such as metal properties, semiconductor characteristics. But the dynamic process under high pressure can not be detected. To study the dynamic process under high pressure, the carrier parameters under high pressure must be detected. Hall effect can reflect the electrical transport behavior of charged particles. Carrier concentration, mobility, Hall coefficient, magnetoresistance can be obtained by Hall effect measurements. These parameters are necessary to analysis the dynamic process under high pressure.In the zinc blende structure of HgTe, the decrease of carrier concentration indicates that the originally overlapped valence band (г8 state) and conduction band (г6 state) separates under pressure. The increase of mobility means the interband resonant scattering reduces with pressure. Further, it can be deduced that the originally overlapped valence band (г8 state) and conduction band (г6 state) of HgTe separates with pressure, corresponding with the above conclusion obtained from the carrier concentration. The zinc blende structure of HgTe is N-type semiconductor.In the pressure range of 1.0 to 1.8 GPa, the Hall coefficient was positive. Note that several structures of HgTe coexisted in this pressure range, therefore it is reasonable to conclude that defects would be formed and make a large contribution to the hole conduction. As the pressure increasing, the coordination number of HgTe increases from 4 to 4+2, to 6, and then to 5+3. The increase of coordination number needs the relative movement of atoms. To the cinnabar structure, the dominant carrier changes from electron to hole at 5.63 GPa, above which the carrier concentration increases with pressure. While the increase rate reduced in the area near 7.68 GPa. It suggests that in the compression process, the Hg atom moves mainly with pressure. Then the Te atom moves quickly with pressure in the area near the phase transition completion.For rocksalt and Cmcm phases of HgTe, the ionized impurity concentration increases with pressure. This would lead to a decrease of mobility with pressure, different to what is actually observed. Consequently, the polar optical scattering of rocksalt and Cmcm must decrease with pressure.The pressure dependence of Hall coefficient, carrier concentration and mobility were found the discontinuities. They were quite consistent with the phase transition pressures of HgSe. Theoretical calculations and experimental results found that Hg atoms to move faster than the Se atoms move from the zinc blende structure of HgSe to the cinnabar process. The Se atoms move faster than the Hg atoms from the cinnabar structure of HgSe to the rock salt phase process. There is N-type semiconductor range during the phase transition from the cinnabar structure to the rock salt phase. Rock salt phase and the Cmcm phase of HgSe are P-type semiconductor phase. For the zinc blende structure of HgS, the resistivity increased with pressure, while the carrier concentration and mobility decreased with pressure. It can conclude that the carrier concentration and the mobility decrease as the pressure increases results in the resistivity increase. The zinc blende phase of HgS is P-type semiconductor. For the cinnabar phase of HgS, from 5.4GPa to 14.6GPa, only the resistivity was measured. The carrier concentration and the mobility were measured at the range of 14.6-25GPa. This indicated two phase coexistence from 14.6GPa to 25GPa. The resistivity decreased mainly due to the increase of carrier concentration. For rock salt phase of HgS, the change of the carrier concentration has a positive contribution to the decrease of resistivity. However, the change of the mobility has a negative contribution to the decrease of resistivity. So the decrease of resistivity was mainly due to the increase of carrier concentration with pressure increases.In conclusion, we established the in situ Hall effect measurement under high pressure. The carrier behavior of HgX (X=S,Se, Te) under high pressure has been studied using the new developed high-pressure Hall effect measurement technology.