硅掺杂MOCVD氧化镓中的非故意掺杂效应:浅施主态

Unintentional doping effect in Si-doped MOCVD β-Ga_(2)O_(3) films:Shallow donor states

本文利用MOCVD外延生长了不同载流子浓度的高质量β-Ga_(2)O_(3)薄膜并通过变温霍尔测量和二次离子质谱(SIMS)分析研究了薄膜中的浅施主态.通过拟合提取出薄膜中存在的两个电离能分别为~36和~140 meV的施主能级.进一步研究发现非故意掺杂(UID)效应对这两个能级都有影响:第一个施主能级不仅来源于硅掺杂也来源于非故意碳掺杂取代Ga位,第二个施主能级主要来源于与非故意掺杂氢相关的双电荷缺陷.通过分析生长条件与施主态之间的关系结合密度泛函理论计算我们发现在生长过程中降低氧分压可能有助于降低UID效应.该工作为硅掺杂MOCVDβ-Ga_(2)O_(3)薄膜载流子浓度的精确控制奠定了基础.

High-quality β-Ga_(2)O_(3) films were epitaxially grown by using metalorganic chemical vapor deposition(MOCVD)with different donor concentrations,and their shallow donor states were investigated by the temperature-dependent Hall measurement and secondary ion mass spectroscopy(SIMS)analysis.Two donor levels with ionization energies of~36 and~140 meV were extracted.It is found that the unintentional doping(UID)effects in MOCVD contribute substantially to both these two levels:the first donor level may come not only from silicon doping but also from unintentional substitution of carbon for Ga sites,and the second donor level probably comes from doubly charged defects related to unintentional H doping.By analyzing the relationship between the growth conditions and donor states,combined with density functional theory calculations,it is found that reducing the oxygen partial pressure during the growth might be a feasible way to reduce the UID effect.This work paves the way to the precise control of carrier density in Si-doped MOCVD β-Ga_(2)O_(3) films.