Measuring femtosecond lifetimes of free charge carriers in gallium arsenide

Peculiarities of the measurement of femtosecond lifetimes of free charge carriers in gallium arsenide grown by the method of molecular beam epitaxy are considered. The carrier lifetime is determined by a variant of the pump-probe method in which the pumping and probing radiation beams are incident onto the semiconductor sample surface at the Brewster angle. The proposed variant ensures the detection of a change in the induced refractive index even in the case of very small response signals, thus providing for a high sensitivity of measurements. It is shown that the relative signal changes near the Brewster angle reach a maximum level.