Research Of Gallium Arsenide Photoelectric Properties And Carrier Dynamics In The Terahertz Waveband

In recent years,countries around the world have carried on extensive researches aiming at terahertz(namely THz)science and technology which is located in the photoelectric cross subject and achieved fruitful results.THz waves have a huge potential application in many fields,such as object’s imaging and detection,environmental monitoring,medical health,mobile communication,aviation and so on.At present,the related devices are scarce in the THz fields,and to this end,we try to use THz waves to act on gallium arsenide(namely GaAs)semiconductor materials and research its related properties.GaAs is one of the second generation semiconductor materials which belongs to sphalerite structure,and it has a direct band gap of double energy valleys and high mobility applying widely in microelectronics and photoelectronics.The combination of GaAs material and THz technology can provide novel ideas for design of THz devices.In this paper,we have researched the spectrum feature of GaAs sample using terahertz time domain spectroscopy(namely THz-TDS)technology in the THz waveband.Using Fourier transform makes its time domain spectrum convert into frequency domain spectrum,and processing the relevant data obtains GaAs sample’s relevant optical and electrical parameters in the frequency range of 0.6～4.0 THz:refractive index,extinction coefficient,absorption coefficient,relative dielectric constant,dielectric loss and conductivity of GaAs.The value of refractive index imaginary part,complex dielectric constant imaginary part and dielectric loss are small,which show that GaAs sample has good dielectric properties in THz wave band.The numerical amplitude of GaAs sample’s conductivity in negative 11 orders of magnitude shows poor electrical conductivity and good semi-insulating of GaAs sample.At the same time,we have studied the carrier ultrafast dynamics of GaAs sample’s light activated layer employing optical-pump terahertz-probe(namely OPTP)technology.We find that GaAs sample’s transmittance of THz waves will decrease through increasing the laser energy or strengthening the pump energy.It is mainly caused by the rising of carrier number in the light activated layer,which leads to enhance THz waves absorption by GaAs sample.But not the bigger of laser energy and pump energy the better,too big numerical value of them may give rise to mutation of material intrinsic nature and result in rapid enlargement of THz waves transmittance.Finally,we have investigated GaAs sample’s carrier ultrafast relaxation process and the absorption bleaching effect under the condition of optical pump.The former is mainly composed of non-equilibrium carrier’s initial inelastic scattering process and carrier’s recombination process.The carrier initial scattering time and carrier effective lifetime of recombination process are 33.21ps and 2.05ns,respectively.We fit carrier relaxation recombination process adopting the exponential function model and acquire 2.5ns of carrier lifetime of its recombination process which is similar to 2.05ns of the carrier effective lifetime that is calculated.We also point out that the radiative recombination plays a leading role among the carrier recombination mechanisms.The latter,the absorption bleaching effect of GaAs carrier,is caused by carriers’internally scattering of GaAs within the higher THz waves energy.