Polarity Inversion of Ga‐Polar GaN Surfaces by Exposing to Mg and NH3 in Metal–Organic Vapor Phase Epitaxy
Polarity Inversion of Ga‐Polar GaN Surfaces by Exposing to Mg and NH3 in Metal–Organic Vapor Phase Epitaxy
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DOI：
10.1002/crat.202200086
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发表时间：
2022-09
影响因子：
1.5
通讯作者：
Chengguo Li
中科院分区：
文献类型：
--
作者：
Chengguo Li
报道了通过将Ga极性表面同时暴露于Mg和氨流来进行从Ga极性到N极性的极性反转（PI）的金属有机气相外延过程。该工艺与传统的Mg重掺杂技术不同，其通过在PI的Ga极性表面上有意地预沉积富Mg薄层来实现。通过在700 °C下曝光900 s，在随后的GaN过生长中实现具有光滑表面的完整PI。原子力显微镜和压电力显微镜的表征表明，极性的变化经历了同时与金字塔形成后，15nm厚的GaN过度生长。Mg的电子色散谱图表明在再生长界面和PI域边界处的高Mg浓度。据信富Mg薄层在暴露过程之后覆盖表面并在随后的生长中释放Mg掺杂剂，导致GaN覆盖层中的高Mg掺入并因此诱导PI。在N极性GaN覆盖层中实现了空穴浓度为2.7 × 1017 cm−3的P型导电。还证明了这种PI技术可以用于在Ga极性主体上具有反向N极性接触层的混合极性结构的紫外发光二极管的生长。
A metal–organic vapor phase epitaxy process of polarity inversion (PI) from Ga‐ to N‐polar is reported by exposing the Ga‐polar surface simultaneously to Mg and ammonia flows. This process differs from the conventional Mg heavy‐doping technique by intentionally predepositing a Mg‐rich thin layer on the Ga‐polar surface for PI. A full PI with a smooth surface in the subsequent GaN overgrowth is achieved by an exposure process for 900 s at 700 °C. Atomic force microscopy and piezo‐force microscopy characterizations reveal that the polarity change undergoes simultaneously with pyramid formation after ≈15 nm thick GaN overgrowth. The electron dispersion spectroscopy mapping of Mg indicates high Mg concentrations at the regrowth interface and in the PI domain boundary. A Mg‐rich thin layer is believed to cover the surface after the exposure process and release Mg dopants in the subsequent growth, leading to a high Mg incorporation in the GaN overlayer and therefore inducing PI. P‐type conduction with a hole concentration of ≈2.7 × 1017 cm−3 is achieved in the N‐polar GaN overlayer. It is also demonstrated that such a PI technique can be employed in the growth of a hybrid polarity structured ultraviolet‐light‐emitting diode with a reversed N‐polar contact layer on a Ga‐polar main body.