Measurement of excitonic and bimolecular radiative processes in quantum wells

The quantum-confined Stark effect has been studied extensively in both emission and absorption processes.1–6 In the case of emission, it has been observed that the luminescence intensity decreases with increasing field and completely quenches even at moderate fields.1 It has been proposed by several workers that the quenching is from an increase in lifetime caused by the polarization of the carriers by the electric field and the competition between radiative and nonradiative (including field-induced tunneling3 and enhanced photocurrent4) processes. It has also been reported that the quenching rate is dependent on the intensity of excitation.1 However, there has not yet been a consistent explanation for the magnitude of the quenching and its excitation-intensity dependence. In this paper we present a complete spectroscopic study that clearly indicates that luminescence quenching is attributable to the field-enhanced dissociation of excitons into free carriers.