Four types of HV-LEDs with different isolation trench width were presented. The isolation trench with an oblique angle of 45.6 degrees was obtained using a combination of Cl-2/BCl3 plasma chemistry and a thermally reflowed photoresist mask layer, enabling conformal metal lines coverage across the isolation trench. The effect of isolation trench width on the optical and electrical characteristics of HV LEDs was also investigated. A quantitative model was developed to analyze light coupling propagation phenomenon occurring within HV LEDs. The suppression of light coupling propagation among adjacent LED cells was achieved by extending isolation trench width from 3.81 pin to 12.30 mu m, which improved light extraction efficiency and thus increased light output power of HV LEDs. However, the significantly increasing loss of MQW active region area, which was caused by further extending isolation trench width from 12.30 mu m to 40.49 mu m, decreased light output power of HV LEDs. (C) 2016 Elsevier B.V. All rights reserved.