Electrical Transport Properties Of InP Under High Pressure

Indium phosphide(InP)is a typical ?-? compound semiconductor material,and one of the new semiconductor materials after Si,GaAs.It has large carri-er concentration,high electron drift speed and other advantages at normal pressure conditions.Comparing with Si and GaAs semiconductor materials,it has chatacter-istics of high electron average velocity and high thermal conductivity,which makes InP widely applicate in optical communication devices,monochromatic lasers,mod-ulators and detectors.However,in the field of electrical properties under pressure might well repay investigation.In this thesis,the micro-circuit is integrated by the technique of manual wiring on diamond anvil cell(DAC).The pressure are generated by DAC device,combined with in situ AC impedance spectroscopy and in situ resistivity measurements,and theoretical calculation method.We analysed AC impedance,electrical resistivity,relaxation frequency for ?-? compound semiconductor InP under 25 GPa,and the microscopic mechanism of InP.Detailed experimental and theorecal observations are as following:Firstly,we performed accurately the high-pressure in situ electrical resistivity of InP sample,including compression up to 25 GPa and decompression process.It can be observed that during the compression process the resistivity of sample has a slow rise from 0 GPa to 2.8 GPa and a slow decline from 2.8 GPa to 4.4 GPa.Specially,after 4.4 GPa the electrical resistivity sharply decreased by nine orders of magnitude.Obviously,it can be determined that sample occurs phase transition under pressure.That is because of the atomic position rearrangement of InP sample caused carrier concentration increasing and conductivity enhancing during phase transformation under high pressure.While,during the decompression process,the resistivity increase about five orders of magnitude was observed at 0 GPa,which means that the phase transition of InP sample is reversible.Secondly,a performance is carried out on InP sample of the temperature de-pendence of in situ electrical resistivity measurements under high pressure in order to prove controversial metallization transition.The result shows that the electrical resistivity decreased with increasing temperature before 2.78 GPa,which shows a semiconductor behavior.After 2.78 GPa,the electrical resistivity of sample increases with temperature,which shows a metallic behavior.Therefore the structural phase transition of the InP sample is a typical transition of the semiconductor to metal.We fitting the conduction activation energy of the InP according to the Arrhenius for-mula.In the rang of 110 K-200 K,the conduction activation energy is relatively low.Thus,the carriers easily be excited to a lower impurity level.Between 200K-285K,the conduction activation energy is relatively high,the carries can not be excited to higher impurity level.When the pressure increases to 4 GPa,the different value of two part conduction activation energy approach zero.The typical behavior of a semiconductor properties will disappear,at the same time the appearance of metal characteristics.The AC impedance spectroscopy of InP sample is measured at pressure range of 0-25 GPa.The experimental results indicate that resistance and relaxation strength of InP reach a maximum at 4 GPa.The resistance of InP decreases sharply by two orders of magnitude and the relaxation strength sharply also decreases,when the pressure increases from 4 GPa to 6 GPa.Because the structure of InP has changed under pressure.We also found that the phase transition of InP sample is reversible.Meanwhile,we only observed the bulk transport property in the experiment.Finally,by First Principle Method calculationgs of InP,we obtained the chang-ing of enthalpy difference with the pressure.When the pressure reaches 4 GPa,the space structure of InP changed from zb phase transforms into the Fm3m.The volume collapsed 19.5%at the same time.The calculation of energy band structure explains that resistivity has a slow increase before 4 GPa,due to the band gap widen increase with pressure.In the meantime,the band gap across the Fermi level,?phase of InP is metallic.