Ultrafast carrier dynamics in InGaAsP grown by He-plasma-assisted epitaxy

We perform dual-wavelength pump–probe measurements on InGaAsP grown by He-plasma-assisted molecular beam epitaxy with Be doping concentrations ranging from 0 to 6×1018 cm−3. The material response times obtained vary from 1 to >70 ps depending on doping concentration, pump pulse energy, and probe wavelength. A two-trap-level rate equation model is presented to explain the various response times observed, and trap densities of 2.5×1017 and 12×1017 cm−3, electron-capture cross-sections of 12×10−15 and 2.8×10−15 cm2, and hole-capture cross-sections of 1.4×10−16 and 1.8×10−15 cm2 are derived by fitting the experimental data. Dual-pulse pump–probe measurements indicate that a fast repeated switching on a ∼10 ps timescale using Be-doped materials can be achieved despite the slow hole-capture rate associated with one of the trap levels.