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High performance GaN based light-emitting diodes with a novel patterned SiO2/Al2O3 passivation layer

2026-06-27 16:45:51 admin

In the field of solid-state lighting, high-performance GaN based LEDs have received widespread attention as potential light sources and have been widely applied in various emission bands such as ultraviolet and visible light. Improving the light extraction efficiency of GaN based LEDs is an important prerequisite for further promotion and application.

However, due to the total reflection phenomenon at the interface between LED and air, the current light extraction efficiency is still very low. Considering the refractive index difference between GaN and air, the critical angle of total reflection c from the chip to the air is only 24.6 ° which reflects most of the light back into the LED chip and is absorbed and converted into heat by the epitaxial layer, greatly reducing the light extraction efficiency. However, if the angle of light emission is less than c, then the light emitted by the LED can freely enter the air. In view of this, some current research aims to improve light extraction efficiency by changing the optical circuit in the device. Common methods include introducing distributed Bragg reflectors (DBR), photonic crystal structures, patterned substrates, and surface passivation.

In recent years, researchers have combined theoretical and experimental studies to investigate the effects of different types of surface passivation layers on the optical and electrical properties of LEDs. Traditional GaN based LEDs with SiO2 passivation layers have been widely used. Chang et al. demonstrated that SiNx thin films prepared by electron cyclotron resonance chemical vapor deposition at room temperature can passivate GaN based LEDs. The experimental results indicate that SiONx prepared by plasma enhanced chemical vapor deposition (PECVD) method can serve as a passivation layer for anti reflection. To enhance the luminescence intensity, Su et al. used hydrogen sulfide to passivate the surface of AlGaInP LEDs. And So et al. noticed that under the condition of constant reflux temperature, the diameter of the bottom of the hemisphere increases with increasing reflux time. With the help of photolithography technology, we used HF to remove the passivation layer on the electrode surface without damaging the surface. The I-V curve and LOP measurement of LED chips were completed by the FitTech IPT6000 LED chip/wafer testing system, and the reverse leakage current IR was measured by a microwave probe station.

Figure 3 (a) shows the I-V characteristics of LEDs with different structures, namely: 0-minute reflow patterned SiO2/Al2O3 passivation layer (sample A); 5-minute reflow graphic SiO2/Al2O3 passivation layer (sample B); 7-minute reflow graphic SiO2/Al2O3 passivation layer (sample C); 9-minute reflow graphic SiO2/Al2O3 passivation layer (sample D); Reflux patterned SiO2/Al2O3 passivation layer for 11 minutes (sample E); And the traditional SiO2 passivation layer (as a reference). Due to the same epitaxial structure, the I-V characteristics of these six LEDs are almost the same, with a forward voltage of 3.1V under an input current of 60mA. Figure 3 (b) shows the photoluminescence (EL) characteristics of these LEDs, with a peak wavelength of 460nm and high output power from Sample D.