Low-frequency noise and charge transport in light-emitting diodes with quantum dots

Abstract

In this experimental study, we have compared low-frequency (LF) noise and transport characteristics of light-emitting diodes (LEDs) with InAs quantum dots embedded in the In0.15Ga0.85As matrix with diodes of similar epitaxial structure without dots. Quantum dot (QD) and quantum well (QW) diodes have the p-i-n structure. At cryogenic temperatures, the LEDs with quantum dots exhibit pure excess tunneling transport mechanism, which originates from the energy levels introduced by quantum dots into the band gap of the intrinsic region. In the LEDs without quantum dots, an excess tunneling current was observed for small current densities. At a higher bias, another transport mechanism dominates, whose features can be explained by the Fowler-Nordheim (FN) tunneling. The low-frequency noise associated with the excess tunneling current is of 1∕f type and its power spectral density depends on the bias as S1∝I. In the diodes without dots, the relation S1∝I2 is valid at the bias, where the current transport mechanism is of Fowler-Nordheim type. In both cases, the considered noise spectral densities do not depend on temperature. We derived the explanation of the observed noise features for the QD and the QW devices on the basis of formulas for fundamental and nonfundamental noise sources, respectively. We measured the LF noise of the light emitted by idodes at room temperature and it appeared that it is a shot noise, which is not correlated with electrical noise.