牺牲Ni退火对硅衬底GaN基发光二极管p型接触影响的研究

Effects of Ni-assisted annealing on p-type contact resistivity of GaN-based LED films grown on Si(111) substrates

本文通过在硅衬底发光二极管(LED)薄膜p-GaN表面蒸发不同厚度的Ni覆盖层,将其在N2:O2=4:1的气氛中、400℃—750℃的温度范围内进行退火,在去掉薄膜表面Ni覆盖层之后制备Pt/p-GaN欧姆接触层.实验结果表明:退火温度和Ni覆盖层厚度均对硅衬底GaN基LED薄膜p型欧姆接触有重要影响,Ni覆盖退火能够显著降低p型层中Mg受主的激活温度.经牺牲Ni退火后,p型比接触电阻率随退火温度的升高呈先变小后变大的规律,随Ni覆盖层厚度的增加呈先变小后变大随后又变小的趋势;经过优化后,当Ni覆盖层厚度为1.5nm,退火温度为450℃,Pt与p-GaN比接触电阻率在不需要二次退火的情况下达到6.1×10-5Ω·cm2.

Different thick Ni layers are deposited on the GaN-based LED films grown on Si（ 111 ） substrates, then LED films are annealed at 400℃--750 ℃ in the atmosphere of N2： O2 =4： 1. The Pt / p-GaN contact layer is prepared after removing the Ni-capping layer. It is found that annealing temperature and thickness of Ni-capping layer each have an important influence on the p-type contact of GaN-based LED film. The Ni film can significantly reduce the activation temperature of Mg aceeptor of the p-type GaN. The characteristic of p-type contact of Ni-capping sample becomes better first then turns worse with annealing temperature and it become better then turns worse and then better with Ni-eapping thickness. After optimization, the specific contact resistivity of Pt/p-GaN in the ease of no second annealing can reach 6. 1 × 10-5 Ω·cm2, when Ni-eapping layer thickness is 1.5 nm and its annealing temperatune is 450 ℃.