Improvement of blue InGaN light-emitting diodes with gradually increased barrier heights from n- to p-layers

Abstract

The advantages of blue InGaN light-emitting diodes (LED) with the active region of gradually increased barrier heights from n- to p-layers are studied. The energy band diagram, hole concentration, electrostatic field near the electron blocking layer (EBL), and the internal quantum efficiency (IQE) are investigated by Crosslight simulation program. The simulation results show that the structure with gradually increased barrier heights has better performance over the equal one, which can be attributed to the mitigated polarization effect near the interface of the last barrier/EBL due to less interface polarization charges. Moreover, reduced barrier height toward the n-layers is beneficial for holes injection and transportation in the active region. As a result, holes are injected into the active region more efficiently and distributed uniformly in the quantum wells, with which both the IQE and the total lighting power are increased. Although it can lead to the broadening of the spontaneous emission spectrum, the increase is slight such that it has little effect on the application in solid-state lighting.

Keywords

InGaN / light-emitting diodes (LED) / polarization effect / gradual barrier height

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant Nos. 60976042 and 10990103), the National Basic Research Program of China (Nos. 2010CB923204 and 2012CB619302), and the China Postdoctoral Science Foundation (No. 20100480064). The authors are also grateful to Mr. M. Yang from Crosslight Software Inc. for technical assistance.

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2014 Higher Education Press and Springer-Verlag Berlin Heidelberg