Radiative emission rate modulation in semiconductor heterostructures coupled to a mirror: A probe of ballistic electron mean free path

Absolute electroluminescence intensities of InP/InGaAs heterostructures are monitored as a function of the position of the active layer from a mirror deposited on the semiconductor surface. The strong observed modulation is explained in terms of confinement of the electromagnetic field in the semi-infinite cavity delimited by the reflecting interface. This effect is shown to be a powerful probe of electron spatial distributions in the direction perpendicular to the layer plane, which allows minority ballistic electron mean free path, and hence femtosecond scattering times, to be precisely measured.