Growth and Characteristics of n-VO2/p-GaN based Heterojunctions

n-VO2/p-GaN based oxide-nitride heterojunctions were realized by growing high quality VO2 films with precisely controlled thickness on p-GaN/sapphire substrates by oxide molecular beam epitaxy(O-MBE).The high crystalline quality of the n-VO2/p-GaN heterojunctions were confirmed by X-ray diffraction(XRD)and scanning electron microscope(SEM)analysis.The phase transition characteristics of the as-grown n-VO2/p-GaN heterojunctions were systematically investigated by temperature-dependent resistivity and infrared transmittance measurements.The results indicated that an excellent reversible metal-to-insulator(MIT)transition is observed with an abrupt change in both resistivity and infrared transmittance(IR)at 330 K,which was lower than the 341 K for bulk single crystal VO2.Remarkably,the resistivity-temperature curve was well consistent with that obtained from the temperature dependent IR transmittance.Meanwhile,the current-voltage characteristics originated from the n-VO2/p-GaN interface were demonstrated both before and after MIT of VO2 overlayer,which were attributed to the p-n junction behavior and Schottky contact character,respectively.The design and modulation of the n-VO2/p-GaN based heterostructure devices will benefit significantly from these achievements.

Effect of TMGa flux on GaN films deposited on Ti coated on glass substrates at low temperature

Highly c-axis-oriented GaN films were deposited on Ti coated glass substrates using low temperature electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition system(ECR-PEMOCVD)with trimethyl gallium(TMGa)as gallium source.The influence of TMGa flux on the properties of GaN films were systematically investigated by reflection high energy electron diffraction(RHEED),X-ray diffraction analysis(XRD),atomic force microscopy(AFM)and Raman scattering.The GaN film with small surface roughness and high c-axis preferred orientation was successfully achieved at the optimized TMGa flux of 1.0 sccm.The ohmic contact characteristic between GaN and Ti layer was clearly demonstrated by the near-linear current-voltage(I-V)curve.The GaN/Ti/glass structure has great potential to dramatically improve the scalability and reduce the cost of solid-state lighting light emitting diodes.

基于KR增硅和转炉加硅石造渣的低硅铁水脱磷技术

针对转炉低硅铁水炼钢过程中存在的热量不足和成渣困难导致脱磷率低下的问题,通过工业试验,研究不同硅含量铁水在冶炼过程中的终点温度、热剂-硅铁量、废钢及矿石用量关系,并结合KR增硅技术和转炉加硅石造渣技术。结果表明,在转炉中添加硅铁时,铁水的化学热少,炉内温度前期上升速率慢,石灰加入量少且不易熔化,不利于前中期脱磷和后期渣的形成,但硅铁在KR熔炼良好,吸收率接近100%;低硅铁水(w(Si)≤0.3%)的脱磷由82.3%增加至87.7%。