Abstract

We have demonstrated the applicability of sensitive picosecond population modulation methods to characterize GaAs interfaces in a MBE-grown GaAs/GaInP double heterojunction and the free GaAs surface with emphasis on free carrier confinement and interface recombination. Two synchronously pumped mode-locked cw dye lasers (DCM) were used for excitation and probing, the former electro-optically modulated at near 10 MHz, and the change in time delayed transmission or reflection of the probe beam from the sample was detected by phase sensitive electronics. In this way optically induced changes less than 1×10⁻⁷ in magnitude could be detected as shown earlier in the pioneering work of Heritage, Levine and co-workers in Raman gain spectroscopy (1). The induced changes were spectrally and temporally resolved near the E_o+Δ_o interband transition from the spin-orbit split-off band to the conduction band edge in GaAs, and near the fundamental edge in Ga_.47In_.53P. These two critical point energies differ by less than 100 meV at 77K and were thus conveniently accessible by the same dye laser in the visible (~6400 A).

© 1982 Optical Society of America