| Abstract: | The tilted energy band in the multiple quantum wells(MQWs) arising from the polarization effect causes the quantum confined Stark effect(QCSE) for 0001] oriented III-nitride-based near ultraviolet light-emitting diodes(NUV LEDs). Here, we prove that the polarization effect in the MQWs for NUV LEDs can be self-screened once the polarization-induced bulk charges are employed by using the alloy-gradient In_xGa_(1-x)N quantum barriers. The numerical calculations demonstrate that the electric field in the quantum wells becomes weak and thereby flattens the energy band in the quantum wells, which accordingly increases the spatial overlap for the electron-hole wave functions. The polarization self-screening effect is further proven by observing the blueshift for the peak emission wavelength in the calculated and the measured emission spectra. Our results also indicate that for NUV LEDs with a small conduction band offset between the quantum well and the quantum barrier,the electron injection efficiency for the proposed structure becomes low. Therefore, we suggest doping the proposed quantum barrier structures with Mg dopants. |
