1. 1 Fig. 3. HRXRD omega/2theta scans of single-, dual-, and step-stage MQW structures.

2. Fig. 4. EL spectra of the dual-stage MQW LED and step-stage MQW LED at 350 mA. The inset is the shift in peak emission energy as a function of injection current in dual- and step-stage LED. Wavelength & EL Intensity 2

3. Fig. 5. Forward– characteristics of the dual-stage MQW LED and stepstage MQW LED. Forward voltage & Current 3

4. Fig. 6. Output powers and EQEs as functions of injection current for the dualstage MQW LED and step-stage MQW LED. Output power & EQE 4

5. CONCLUSION The light output power of the step-stage LED are 363.8mW and EQE of 36.7%, which represents a 23% increase over that of dual-stage LED. Due to the indium-stepwise-doped EIL could be a better prestrain layer and could provide an easier electron-tunneling structure for the electrons. 5

6. REFERENCES Hsiao-Chiu Hsu, Yan-Kuin Su, Fellow, IEEE, Shyh-Jer Huang, Chi- Yao Tseng, Chiao-Yang Cheng, and Kuan-Chun Chen,” IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 23, “,NO. 5, MARCH 1, 2011. 6