Producing deep UV-LEDs in high-yield MOVPE by improving AlN crystal quality with sputtered AlN nucleation layer

Abstract

High-quality AlN layers with low-density threading dislocations are indispensable for high-efficiency deep ultraviolet light-emitting diodes (UV-LEDs). In this work, a high-temperature AlN epitaxial layer was grown on sputtered AlN layer (used as nucleation layer, SNL) by a high-yield industrial metalorganic vapor phase epitaxy (MOVPE). The full width half maximum (FWHM) of the rocking curve shows that the AlN epitaxial layer with SNL has good crystal quality. Furthermore, the relationships between the thickness of SNL and the FWHM values of ( 002) and ( 102) peaks were also studied. Finally, utilizing an SNL to enhance the quality of the epitaxial layer, deep UV-LEDs at 282 nm were successfully realized on sapphire substrate by the high-yield industrial MOVPE. The light-output power (LOP) of a deep UV-LED reaches 1.65 mW at 20 mA with external quantum efficiency of 1.87%. In addition, the saturation LOP of the deep UV-LED is 4.31 mW at an injection current of 60 mA. Hence, our studies supply a possible process to grow commercial deep UV-LEDs in high throughput industrial MOVPE, which can increase yield, at lower cost.

Comprehensive study of crystalline AlN/sapphire templates after high-temperature annealing with various sputtering conditions

“…To date, the reported full width at half maximum (FWHM) values of (0002)-and (10 2)-plane of AlN grown by MOCVD have been reduced to 79 and 206 arcsec [6] . Meanwhile, due to the large lattice and thermal expansion coefficient mismatches between AlN and sapphire, AlN grown on sapphire by metal-organic chemical vapor deposition (MOCVD) system still suffers from the TDD higher than 10 8 cm -2 [7] , although many methods have been proposed to reduce the TDD of AlN films grown on sapphire, such as periodical high/middle-temperature AlN growth method [8] , ELOG method [9] , the nano-patterned sapphire substrates (NPSS) [10] , and two-phase growth method [11] . Moreover, the serious prereaction of trimethylaluminum (TMAl) and ammonia (NH 3 ) [12] ,   the poor uniformity of temperature distribution in the chamber, and rapid consumption of heater at high temperature (HT) limit the yield of AlN films by MOCVD with small-size reactor and lead to the high cost of UVC LEDs.…”

High-performance AlGaN-based deep ultraviolet light-emitting diodes with different types of InAlGaN/AlGaN electron blocking layer

“…[6][7][8] The enhancement of EQE is impeded by high threading dislocation density (TDD) and low carrier injection efficiency (CIE) in DUV LEDs. [9][10][11] Several advanced techniques have been proposed to reduce the TDD, [12][13][14][15][16][17][18][19][20] but the CIE still remains low. Therefore, it is crucial to enhance the CIE for the realization of high-performance DUV LEDs.…”

Novel Method for Improving Process Repeatability of the AlN Buffer Layer

“…Deep ultraviolet light-emitting diodes (DUV-LEDs) are widely applied in sterilization, water purification, medicine and biochemistry, and analytical optical instrumentation. − At present, DUV-LEDs are mainly obtained through epitaxial growth. − In the film structure of DUV-LED epitaxy, the AlN film plays a good transition role between sapphire and the AlGaN film and serves as a template for the growth of AlGaN. , Since the homoepitaxial technology is not yet mature, commercialized, large-size AlN substrates are very expensive and have unstable performance. Therefore, the epitaxy of DUV-LEDs is mainly realized on heterogeneous substrates, and sapphire is the most commonly used foreign substrate. − However, the inevitable lattice mismatch between AlN and sapphire is still a technical problem in epitaxial growth .…”