Fig. 1. Fabrication process of floating InGaN/GaN QW microdisk devices，the finally structures of device I，II and III are shown in the box

Fig. 2. SEM images of InGaN/GaN QW devices

Fig. 3. EL spectra under the different injection currents，inset shows the enlarged spectra under 2 mA and luminous images of three types of devices

Fig. 4. Electrical and spectral detail characteristics of different devices

Fig. 5. The surface current distribution simulation of two types of microdisks