Ingale Alka, Pal Suparna, Dixit V K, Tiwari Pragya
Laser Physics Application Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India.
J Nanosci Nanotechnol. 2007 Jun;7(6):2186-91. doi: 10.1166/jnn.2007.792.
Variation of depth within a single etching spot (3 mm circular diameter) was observed in nanoporous GaN epilayer obtained on photo-assisted electrochemical etching of n and p-type GaN. The different etching depth regions were studied using microRaman and PL(yellow region) for both n-type and p-type GaN. From Raman spectroscopy, we observed that increase in disorder is accompanied by stress relaxation, as depth of etching increases for n-type GaN epilayer. This is well corroborated with scanning electron microscopy results. Contrarily, for p-type GaN epilayer we found that for minimum etching depth, stress in epilayer increases with increase in disorder. This is understood with the fact that as grown p-type GaN is more disordered compared to n-type GaN due to heavy Mg doping and further disorder leads to lattice distortion leading to increase in stress.
在通过n型和p型GaN的光辅助电化学蚀刻获得的纳米多孔GaN外延层中，观察到单个蚀刻点（直径3毫米的圆形）内深度的变化。使用微拉曼光谱和PL（黄色区域）对n型和p型GaN的不同蚀刻深度区域进行了研究。从拉曼光谱中我们观察到，对于n型GaN外延层，随着蚀刻深度的增加，无序度的增加伴随着应力松弛。这与扫描电子显微镜结果得到了很好的证实。相反，对于p型GaN外延层，我们发现对于最小蚀刻深度，外延层中的应力随着无序度的增加而增加。这可以通过以下事实来理解：由于重Mg掺杂，生长态的p型GaN比n型GaN更无序，进一步的无序会导致晶格畸变，从而导致应力增加。
