The role of spontaneous and piezoelectric polarization fields on the spectral and power characteristics of InxGa1-xN/GaN superluminescent light emitting diodes

摘要

The output characteristics of InxGa1-xN/GaN MQW blue SLEDs are investigated using a detailed theoretical model, in which the effects of spontaneous and piezoelectric polarizations are fully considered. By solving the Schrodinger equation in effective mass approximation, Poisson's equation, and two level rate equations with no-k selection wavelength dependent gain self-consistently, the influence of these internal fields on the electrical and optical characteristics of MQW SLEDs under bias conditions have been studied. The spontaneous polarization and the piezoelectric polarization changed with indium molarity in our structure at 2.9-3.2 V biased voltages. Below 3.05 V the blue shift of peaks due to band filing and screening of QCSE, and above 3.05 V red shifting due to device heating are seen obviously. With increasing of indium content and polarization fields accordingly in different modeled SLDs, peaks of spectral radiation power were dropped and diagrams were red shifted at the range of 3.0-4.0 nm under various applied voltages. FWHM of modeled devices raises ? 0.3-0.4 nm with 1 indium content increasing (0.1356 MV/cm polarization field) in three different SLDs with 19.5, 20, and 20.5 indium in QWs. Total light output power of SLDs at 3.2 V dropped 6.22 (7.08 mW) with 1 indium content increasing (according to 0.1356 MV/cm total polarization field).