INTERSUBBAND OPTICAL TRANSIENTS IN MULTI-QUANTUM-WELL STRUCTURES

We show that optical transients due to the intersubband photoionizatio n of the electrons from quantum wells may be observed by inserting a m ulti-quantum-well structure in the space-charge layer of a Schottky di ode. This method provides a direct measurement of the photoionization cross section of a quantum well. The escape probability of the photoex cited electron from the quantum well can thus be unambiguously deduced . Its variation with the electric field may be described by a simple m odel based on the statistical fluctuation of the quantum-well width.