Synthesis Of Zinc Blende GaN Microrods And Its Single Homogeneous LEDs

Ga N is excellent optoelectronic properties with direct and wide bandgap,high mobility,and excellent thermal stability.In recent years,Ga N with zinc-blende structure has been drawn increasing attention due to higher crystallographic symmetry and lower phonon scattering than one with wurtzite.Ga N micro/nanorods which combined the advantages of Ga N and micro/nano materials are emerging as a very promising novel route toward devices for micro/nano-optoelectronics and photonics.Especially,in comparison to conventional 2D thin film LEDs,LEDs based on Ga N micro/nanorods offer many potential advantages.Now in order to adapt to market demand for LED based on micro/nano Ga N,high efficiency,high brightness,and low cost are the fundamental requirements for solid state lighting based on Ga N.To meet these requirements,the key developments today are the use of large area,low cost Si substrates,non-polar Ga N micro/nano materials.In order to solve the high current luminous efficiency droop effect of the traditional wurtzite Ga N-based LED,here,the non-polar c-Ga N microrods(MC)on patterned Si substrate and wurtzite Ga N microrods(MH)with controllable sizes and shapes were synthesized by simple chemical vapor deposition(CVD),which is through regulated temperature,pressure and other conditions.Based on the as-grown Ga N,a low-dimensional structure LED is fabricated.The main results are as follows:(1)Due to the metastable nature of the cubic phase,epilayer-substrate chemical incompatibility and large lattice-mismatch make it difficult to grow pure c-Ga N because the h-Ga N composition frequently appeared in the growing c-Ga N micro/nanostructure.To solve this problem,we carry out graphic processing on Si substrate and adjusting the temperature,pressure and other conditions.Here,we report the growth of stress-free c-Ga N MCs with 100% yield on Si(111)substrate by chemical vapor deposition(CVD),and the possible growth mechanism of the Ga N MCs is discussed.From the Ga N MCs,high-performance yellow luminescence(YL)is for the first observed by different temperature photoluminescence spectra and the possible origin of the YL band is investigated.(2)In contrast to the subsequent build device performance,we also synthesized wurtzite Ga N microrods with controllable size,high quality,hexahedron-like morphology,and the detailed structure,morphology and optical properties were analysed.(3)Utilizing the as-grown Ga N,a low-dimensional structure LED is fabricated.Studies on the single c-Ga N homojunction phosphor-free LED show excellent white emission under an operating voltage of 12 V.We have demonstrated the most efficient phosphor-free white MC-LEDs ever reported,which exhibits an internal quantum efficiency of ~99.2% and an output power of ~4.4 m W for a typical operating current of 20 m A and more than 50% stronger than those of conventional h-Ga N homojunction LED.The photoelectrical properties of MC-LEDs exhibit superior luminous and power efficiency to those of MH-LED owing to the ultralow dislocation density and the absence of piezoelectric polarization.