Effect of Substrate Polarity on the Performance Characteristics of InGaN-based Green Light-Emitting Diodes
Vadim P. Sirkeli
Abstract
We report on a numerical study of InGaN-based green light-emitting diodes (LEDs) on polar c-plane (0001) and semipolar (11 $$\bar {2}$$ 2), (11 $$\bar {2}$$ 1), and (10 $$\bar {1}$$ 2) substrates. The simulation results show that the LED on semipolar (10 $$\bar {1}$$ 2) substrate has the lowest turn-on voltage of ~3.6 V compared 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/cm2, the wall-plug efficiencies of 11.5 and 14.7% were achieved for the LEDs on polar c-plane (0001) and semipolar (10 $$\bar {1}$$ 2) substrates, respectively. It was found that the electroluminescence (EL) peak of the green LED on the semipolar (10 $$\bar {1}$$ 2) 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/cm2.