MOCVD生长纯度GaAs中起支配作用的剩余浅杂质研究

<正> 一、引言 众所周知,高纯外延材料是器件制作的基础。但是,在实际工艺过程中,尽管采用高纯源,总不免有不同种类、不同含量的杂质进入外延层。这就是非有意掺杂。MOCVD生长纯度GaAs中非有意掺杂元素主要来源于TMG。在AsH_3-TMG体系MOCVD生长GaAs中,非有意掺杂载流子浓度随As/Ga比变化,并存在由p至n型导电类型的变化。由于AsH_3分压成为导电类型变化的界限,那末,在外延层中起支配作用的电活性杂质就是起着两性杂质作用的Ⅳ族元素。本文根据对不同纯度TMG的比较,结合对外延层的理化分析,认为起支配作用的是C和Si。文中建立了简单的热力学模型,用实验数据确定平衡常数,获得了载流子浓度和类型随输入As/Ga比变化的解析公式,并与实验结果符合良好。生长的GaAs电参数为:N=9×10~(14)cm~(-3),μ=5100cm~2/V·S。

A Study of the Dominant Residual Shallow Impurities in MOCVD Undoped GaAs

GaAs was grown by the MOCVD Process. The results show that the dominant residual shallow impurities are Gabon and Silicon in unintentionally doped GaAs. A simple thermodynamic model, which took Carbon and Silicon to be the amphoteric impurities in GaAs, has was developed for analysis of the effects of As/Ga ratio on the types and concentration of the carrieres. An analytical formula was also obtainted ana the theory agrees well with the expermeatal results. The mobility is 5100cm2/V·s at the carrier concentration N = 9×1014cm-3.