Role of carbon in GaN
Role of carbon in GaN
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DOI：
10.1063/1.1518794
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发表时间：
2002-12-01
影响因子：
3.2
通讯作者：
Götz, W
中科院分区：
文献类型：
--
作者：
Seager, CH;Wright, AF;Götz, W
GaN 样品含有不同浓度的碳并有意掺杂硅，已使用金属有机化学气相沉积在蓝宝石上异质外延生长。这些样品已通过各种电学和光学技术进行了表征，并将所得实验数据与六方氮化镓中取代碳和间隙碳的形成能和电子态的密度泛函理论计算进行了比较。我们发现，在硅浓度超过碳浓度的样品中，碳位于氮取代位点，充当受体并部分补偿材料。然而，当碳密度超过Si时，由于碳占据N和Ga替代晶格位点，GaN变得半绝缘，并且在大约3 eV处出现新的发光峰。计算出的两个位点的碳形成能是费米能级和生长化学计量的强函数。当[C]>[Si]时，前一种依赖性会产生自补偿，因为Ga取代构型（施主态）的形成能变得等于N取代位点的形成能，当费米能级接近中带隙时，有效地固定费米能级。我们的结果表明，GaN 的有效 p 型掺杂只能在富 Ga 生长条件下实现。 (C) 2002 年美国物理研究所。
GaN samples, containing various concentrations of carbon and doped intentionally with silicon, have been grown heteroepitaxially on sapphire using metal-organic chemical-vapor deposition. These samples have been characterized by a variety of electrical and optical techniques, and the resulting experimental data are compared to density-functional-theory calculations of the formation energies and electronic states of substitutional and interstitial carbon in hexagonal GaN. We find that in samples where the silicon concentration exceeds that of carbon, carbon sits in the N substitutional site, acting as an acceptor and partially compensating the material. However, when carbon densities exceed those for Si, GaN becomes semi-insulating due to carbon occupation of both N and Ga substitutional lattice sites, and a new luminescence peak appears at similar to3 eV. Calculated formation energies of carbon in both sites are strong functions of both the Fermi level and growth stoichiometry. The former dependence gives rise to self-compensation when [C]>[Si] because the formation energy of the Ga substitutional configuration (the donor state) becomes equal to that of the N substitutional site, effectively pinning the Fermi level as it approaches midgap. Our results suggest that effective p-type doping of GaN can only be achieved under Ga-rich growth conditions. (C) 2002 American Institute of Physics.