Terahertz Carrier Dynamics In Gallium Antimonide

Ⅲ-Ⅴ semiconductor compounds are widely used in the field of electronic and optoelectronic devices due to its superior electronic and photo-electronic properties.As a member of Ⅲ-Ⅴ compounds,gallium antimonide(Ga Sb)has attracted lots of attentions with its applications in highspeed electronics,microwave and infrared devices,as well as optical fiber communication technology.In addition,Ga Sb is also an ideal material for investigating intervalley electron scattering and Auger recombination effect because of the unique electronic band structure.In this thesis the dynamic characteristics of nonlinear carriers in Ga Sb materials are systematically studied with high power femtosecond laser and terahertz time domain spectroscopy(THz-TDS).The main are as follows:(1)We take the measurement the reflection optical pump-terahertz probe at room temperature for high mobility n-type Ga Sb.The experimental results show that the ultrafast dynamic response of Ga Sb can be described with a single exponential decay process.The corresponding complex optical conductivity of free electrons can be well fitted by the Drude formula.Through the optical measurement,we can obtain the key material parameters of Ga Sb such as photo-induced carrier life time,free electron’s momentum relaxation time,and the carrier concentration,etc.It is found that the photoinduced carriers’ concentration and lifetime in Ga Sb increase significantly with increasing the intensity of pump light.The momentum relaxation time of free electron also increases slightly with changing the pump light’s intensity.The experimental results under strong pumping light show that the nonlinear photoelectrical response of carriers in Ga Sb have a typical phonon bottle-neck effect.(2)With a CW laser pumping at 655 nm and reflection terahertz time-domain spectroscopy,we study the momentum relaxation characteristics of n-type Ga Sb with non-equilibrium state at room temperature.The experimental results show that the momentum relaxation time of free electrons in Ga Sb decreases with increasing of power of CW laser.We think that it is caused by the enhancement of effective electron-phonon scattering intensity.The results obtained in this thesis reveal the basic dynamics laws of photo-induced and free carriers in Ga Sb materials,which is of great significance for the in-depth understanding of the physics of electronic and photoelectric devices based on Ga Sb.