Effect of Substrate Polarity on the Performance Characteristics of InGaN-based Green Light-Emitting Diodes

We report on a numerical study of InGaN-based green light-emitting diodes (LEDs) on polar c-plane (0001) and semipolar (11 (2) over bar2), (11 (2) over bar1), and (10 (1) over bar2) substrates. The simulation results show that the LED on semipolar (1012) substrate has the lowest turn-on voltage of similar to 3.6 V compared to similar to 5.0 V for the polar c-plane LED. It was found that the performance of LEDs on semipolar substrates is superior compared to that of conventional green LED on a polar c-plane substrates due to the reduced impact of polarization effects in semipolar devices. This results in enhanced carrier injection and better carrier balance in the active region. At a current density of 100 A/cm(2), the wall-plug efficiencies of 11.5 and 14.7% were achieved for the LEDs on polar c-plane (0001) and semipolar (1012) substrates, respectively. It was found that the electroluminescence (EL) peak of the green LED on the semipolar (101 (2) over bar) substrate is located at 500.4 nm, which is blueshifted compared to the 530.4 nm peak in the polar c-plane LED. Furthermore, it was established that the semipolar LEDs exhibit better EL peak wavelength stability compared to the polar c-plane LED as the current density increases from 20 to 100 A/cm(2).