喷淋头高度对AlGaN生长的影响

Effect on AlGaN Growth with Showerhead Gap Position in MOCVD

采用GaN材料常用的生长设备金属有机化合物气相沉积(MOCVD)系统,以蓝宝石为衬底,在GaN上沉积Al GaN薄膜。通过调整MOCVD中喷淋头与基座间的距离,探讨喷淋头高度对AlGaN薄膜生长的影响。选择4个喷淋头高度生长样品,利用金相显微镜、原子力显微镜(AFM)和X射线衍射(XRD)对样品进行表征。实验结果表明,在一定范围内,随着喷淋头高度增大,样品表面平滑粗糙度减小,由XRD测试可得此时晶体质量也变好,Al组分线性减少;但继续增大喷淋头高度时,导致预反应过多,Al组分更少,且表面粗糙度增大。

As the main product of blue LEDs,GaN based LED filled in the vacancy of blue LEDs and brought unlimited opportunities for LED applications.In GaN based LEDs,AlGaN film was used as electron blocking layer（EBL） in order to deal with the efficiency droop when it came to large current.The quality of AlGaN film could affect many properties of LED.This paper adopted metal organic chemical vapor deposition system（MOCVD） and grewAlGaN film on sapphire substrate and GaN film.In the MOCVD,we set up four showerhead gap positions to study the effect of showerhead gap position on AlGaN growth.Atomic force microscopy（AFM） and X-ray diffraction（XRD） were used to represent samples.As a result,the surface morphology tests showed that the surface morphology became smoother and the RMS roughness of AlGaN decreased with the increasing of showerhead gap position in the certain range.The quality of crystal became better and the Al composition in AlGaN film became less according to XRD result.However,because of the more severe of prereaction due to higher showerhead gap position,the Al composition became less and the surface roughness became worse.