Investigate Of GaN Nucleation Layer Grown By MOCVD

As the represent of ?-V semiconductors,Gallium nitride(GaN)has wide band gap,high thermal conductivity,high carrier concentration,good chemical stability,high saturated electron mobility and so on,which has been widely used in lighting,microelectronics,communication and so on.At present,high quality GaN films are mainly obtained under hydrogen ambience using “two-step” process.Nitrogen ambience is safer,easier preparation and lower cost compared to hydrogen ambience.It's a research hotspot to get high quality GaN films under nitrogen ambience.In this paper,we focus on the GaN nucleation layer,which has important influence on the quality of GaN films.GaN nucleation layers and films are grown on(0001)sapphire substrate.First,we grow GaN nucleation layer using MOCVD under hydrogen ambience.The effect of nucleation temperature,reactor pressure,?/?,high temperature nitridation before growth and high temperature anneal after growth on surface morphology are investigated respectively.We study the effect of different growth condition on nucleation layer.Then,the effect of different ambience on nucleation layer are investigated.It's found that the GaN nucleation layer tend to form larger islands under hydrogen ambience and tend to form higher density of nucleation islands and thicker nucleation layer under nitrogen ambience.Finally,we study the Raman PL of the GaN films under hydrogen ambience and nitrogen ambience.The compressive stress is found in GaN films.The compressive stress in GaN films is larger under hydrogen ambience.By changing the growth conditions of the nucleation layer,we obtained a series of results.On the one hand,these results explain the nucleation mechanism of GaN nucleation layer.On the other hand,these results will provide good guidance and reference for the growth of GaN films.