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To improve the performance of optoelectronic devices, a high performance wide angle SiO2/Ti3O5 Distributed Bragg Reflector (DBR) mirror was designed and fabricated on double polished sapphire substrate. 17-pairs gradually varied DBR structure was applied in order to acquire a broad stopband reflectivity over 95% from 400 nm to 800 nm, covering the whole visible light region. The DBR mirrors deposited at the backside of optoelectronics devices are also demonstrated to remain a high reflectivity at wide incident angles, which improves the emission efficiency of LEDs and light absorption efficiency of InGaN/GaN photoelectrochemical cell (PEC).

Semi-polar micro-LEDs have gain increasing interests due to the advantages of polarization control and quantum efficiency improvement. In this work, a novel semi-polar (20–21)-plane micro-LEDs array has been designed and manufactured. In comparison with c-plane micro-LEDs, semi-polar micro-LEDs indicate better electrical and optical performance. The relative EQE of semi-polar micro-LEDs remains at 62% under the injected current density of 775.6 A/cm2, which indicates a reduced efficiency droop due to less polarization in MQWs. It has been further proved by a significant reduction of 55% in emission peak blue-shift under the injected current density from 11.1 A/cm2 to 775.6 A/cm2. In addition, the carrier recombination dynamics and spatial light distribution of semi-polar micro-LEDs with different pixel sizes have been studied. Fast recombination lifetime in smaller size semi-polar micro-LEDs indicates a promising way to be used as a high modulation bandwidth light source. Stable and uniform light distribution in a wider range of spatial azimuths further supports for the semi-polar micro-LEDs as a strong candidate for the applications of high-resolution display and high-speed visible light communication.

It is known that the commercialized white light-emitting diodes (WLEDs) depend on phosphor conversion, which is limited by the unbalanced carrier injection in multiple quantum wells (MQWs) and low down-conversion efficiency. To solve these problems, hybrid organic/inorganic III-nitride WLEDs were designed and fabricated based on Rubrene/(InGaN/GaN) MQWs p-n junction. In such new structure, Rubrene can act as yellow–red emitter and play an important role in hole transport layer owing to its high carrier mobility. By optimizing the hybrid LED structure, the charge balance and recombination zone in radiative region were significantly improved. In this work, the optimal hybrid WLED with color coordinates of (0.31, 0.33) shows a maximum current efficiency of 15.22 cd/A with excellent long lifetime stability. The hybrid WLEDs based on organic/inorganic p-n junction were demonstrated with a good performance, which provides an attractive route to achieve high performance phosphor-free WLED sources for microdisplay or large-area WLED applications.

Hybrid white light emitting diodes (LEDs) have been developed utilizing micro-LEDs radiatively pumping down-conversion phosphor materials. The cyan InGaN/GaN multiple quantum wells LEDs with 95 μm in square are fabricated into 4 × 4 pixels as one unit in 4 in wafer by photolithography and inductively coupled plasma etching techniques. The relatively low turn on voltage and low leakage of cyan micro-LEDs indicate good electrical performance. A significant reduction in the efficiency droop characteristics of cyan micro-LED has been observed in comparison with that of standard green LED. Finally, based on a systemic optimization for white emission indexes, high-quality hybrid white light emission has been demonstrated by the combination of blue and cyan micro-LEDs with two types of phosphors, which have a high color rendering index up to 87 at the correlated color temperatures of 6500 K. It also demonstrates a way to adjust the color component by modifying the output power of cyan micro-LED in hybrid LED, showing a promising candidate in a large range of applications including micro-displays, bioinstrumentation, photolithography, and lab-on-chip systems in the future.

We have fabricated the InGaN/AlGaInN multiple quantum wells with lattice-matched AlGaN/InGaN superlattices barriers (SL-MQWs). The lattice-matched superlattices promote the formation of the high-quality MQWs and eliminate the large polarization electric field. Highly excited photoluminescence measurement is performed by Ti-sapphire pulse laser with the maximal carrier density of 1020 cm−3. Under such high carrier density, the conventional InGaN/GaN MQWs (C-MQWs) have an additional nonradiative loss of carriers and suffer from the efficiency droop effect, while slight droop behavior is observed in the SL-MQWs sample. The results show that the substitution of AlGaN/InGaN superlattices as quantum barriers can effectively suppress the droop behavior at highly excited condition.

The mechanisms of reverse leakage in InGaN/GaN multiple-quantum-wells (MQWs) blue and green light-emitting diodes (LEDs) were studied through analyzing the current–voltage ( I–V ) characteristics with the temperature ranging from 50 to 350 K. When the reverse bias V is below 12 V, the leakage current is dominated by the variable-range hopping conduction $(T\rm{ and Poole–Frenkel emission $(T\rm{ > 250\,K)}$ , respectively. As the reverse bias increases $(\vert V\vert \rm{ > 12\,V)}$ , the space-charge-limited conduction mechanism is responsible for the leakage current. It is found that the leakage current is highly associated with the defects density, as well as the trapping capacity of deep level centers; therefore, the lower leakage current of blue LED is mainly attributed to higher thermal activation energy $E_{a}$ due to less deep level centers within GaN/InGaN MQWs structures.