Influence of the backward-pump process on photon-number squeezing in a constant-current-driven heterojunction LED: Transition from thermionic emission to diffusion limits

Physical mechanisms which limit the squeezing bandwidth in a heterojunction light-emitting diode (LED) have been extensively studied both theoreticall y and experimentally. It is proven that our experimental results of pump-cu rrent dependence of the squeezing bandwidth in the constant-current-driven heterojunction LED at room temperature cannot be explained by previous theo retical predictions. We present a theoretical framework, including the effe cts of a microscopic backward-pump (BP) process, generally applicable to a heterojunction LED. Parameters describing the relative significance of the BP process are determined by the measurements of current-versus-voltage cha racteristic and differential resistance of the LED, independent of the nois e measurements. As a consequence, the experimental results can be explained by our model in a unified manner ol er a whole range of injection current, and it is clarified that the pump situation of the LED moves continuously from thermionic emission to diffusion limits with increasing pump current. [S0163-1829(99)09247-4].