Comprehensive Modeling of Superluminescent Light-Emitting Diodes

We present a self-consistent electric and optic model for superluminescent light-emitting diodes (SLED) using 3D finite-element method. The carrier transport is calculated by the drift-diffusion method, which is coupled with the radiative recombination obtained from the solution of Shrodinger-Poison equations self-consistently. The spontaneous emission noise is described by the fundamental theory using the Green's function method. Our model allows 2D treatment of the carrier dynamics and optical confinement on the transverse plane, along with the electronic and optical variation on the longitudinal axis. The theoretical model has been benchmarked with an InP-based edge-emitting SLED. The device has nonidentical quantum wells with broad bandwidth from 1300 to 1600 nm. The results show the importance of 3D effects and demonstrate the validity of the model.

I. Introduction

Superluminescent light-emitting diodes (SLEDs) is a diode in which there is spontaneous emission with amplification, but insufficient feedback for oscillations to build up to achieve lasing action [1]. A superluminescent diode is a light source with properties intermediate between those of a light-emitting diode (LED) and laser diode (LD). Broadband SLEDs are highly desired for applications in optical communication [2], optic sensing and medical instrumentations [3]. Using nonidentical multiple quantum wells (MQWs) is a widely used method to broaden the bandwidth of SLEDs [4]. This scheme includes using the transitions from QWs of different width and composition for broadband purposes. However, nonuniform carrier distribution among the MQWs has been found, and the amplified spontaneous emission (ASE) spectra is sensitive to the sequence of MQWs and separate confinement heterostructure (SCH) [5]. Design and Optimization of the structure of SLEDs for the broad band application has to be conducted with respect to the composition and the thickness of the QWs, and the sequence of QWs as well as the thickness of SCH layers. The modeling and simulation is a cost effective tool to help the process.