Strong enhancement of THz radiation intensity from semi-insulating GaAs surfaces at high temperatures

The temperature dependence of THz radiation from semi-insulating GaAs surfaces excited by ultrashort laser pulses has been studied above room temperature up to 900 K. It is found that the radiation power increases with an increase in temperature and has a peak at ∼500 K, and then decreases with a further increase in temperature. The power radiated at 500 K is more than 30 times stronger than that at room temperature. The enhancement mechanism is discussed in relation to the temperature dependence of the built-in surface electric field.