非故意掺杂GaN薄膜方块电阻与载气中N2比例关系研究

利用金属有机气相外延方法研究了非故意掺杂GaN薄膜的方块电阻与高温GaN体材料生长时载气中N₂比例的关系.研究发现，随着载气中N₂比例的增加，GaN薄膜方块电阻急剧增加.当载气中N₂比例为50%时，GaN薄膜方块电阻达1.1×10⁸Ω/□，且GaN表面平整，均方根粗糙度为0.233nm.二次离子质谱分析发现，载气中N₂比例不同的样品中碳、氧杂质含量无明显差别.随着载气中N₂比 关键词： 半绝缘GaN薄膜 载气 金属有机气相外延 位错

Dependence of GaN film sheet resistance on the N2 carrier gas percentage

In this paper, GaN films are grown by metal organic vapor phase epitaxy. Different N₂ carrier gas percentages were used in the high-temperature growth process of the bulk GaN, and the dependence of sheet resistance on N₂ carrier gas percentage is studied. It is found that the sheet resistance of the GaN film increases dramatically with N₂ carrier gas percentage. When N₂ carrier gas percentage is 50%, the sheet resistance of the GaN film is 1.1×10⁸Ω/sq, and the surface root-mean-square roughness is as small as 0.233 nm. Secondary ion mass spectroscopy measurements reveal that the concentration of carbon and oxygen impurities is almost the same in the samples with different N₂ carrier gas percentage. The density of edge-dislocation-related defects increases with N₂ carrier gas percentage, while the density of screw-dislocation-related defects shows no obvious difference for all the samples. Our results indicate that the increase of the sheet resistance of GaN film is mainly due to the increase of edge threading dislocations, which act as acceptor centers in the GaN material.