A combination of atomic force microscopy （AFM） and scanning electron microscopy （SEM） is used to characterize dislocation etch pits in Si-doped GaN epilayer etched by molten KOH. Three types of etch pits with diff...A combination of atomic force microscopy （AFM） and scanning electron microscopy （SEM） is used to characterize dislocation etch pits in Si-doped GaN epilayer etched by molten KOH. Three types of etch pits with different shapes and specific positions in the surface have been observed,and a model of the etching mechanism is proposed to explain their origins. The pure screw dislocation is easily etched along the steps that the dislocation terminates. Consequently a small Ga-polar plane is formed to prevent further vertical etching,resulting in an etch pit shaped like an inverted truncated hexagonal pyramid at the terminal chiasma of two surface steps. However, the pure edge dislocation is easily etched along the dislocation line,inducing an etch pit of inverted hexagonal pyramid aligned with the surface step. The polarity is found to play an important role in the etching process of GaN.展开更多
This paper reports that the yellow luminescence intensity of N-polar GaN Epi-layers is much lower than that of Ga-polar ones due to the inverse polarity, and reduces drastically in the N-polar unintentionally-doped Ga...This paper reports that the yellow luminescence intensity of N-polar GaN Epi-layers is much lower than that of Ga-polar ones due to the inverse polarity, and reduces drastically in the N-polar unintentionally-doped GaN after etching in KOH solution. The ratio of yellow luminescence intensity to band-edge emission intensity decreases sharply with the etching time. The full width at half maximum of x-ray diffraction of （10-12） plane falls sharply after etching, and the surface morphology characterized by scanning electron microscope shows a rough surface that changes with the etching time. The mechanism for the generation of the yellow luminescence are explained in details.展开更多
The etching characteristics of concave and convex corners formed in a microstructure by the intersection of {111} planes in wet anisotropic etchant are exactly opposite to each other. The convex corners are severely a...The etching characteristics of concave and convex corners formed in a microstructure by the intersection of {111} planes in wet anisotropic etchant are exactly opposite to each other. The convex corners are severely attacked by anisotropic Fetchant, while the concave corners remain unaffected. In this paper, we present a new model which explains the root cause of the initiation and advancement of undercutting phenomenon at convex corners and its absence at concave corners on {110} silicon wafers. This contrary etching characteristics of convex and concave corners is explained by utilizing the role of dangling bond in etching process and the etching behavior of the tangent plane at the convex corner. The silicon atoms at the convex edge/ridge belong to a high etch rate tangent plane as compared to {111} sidewalls, which leads to the initiation of undercutting at the convex corner. On the other hand, all the bonds of silicon atoms pertaining to concave edges/ridge are engaged with neighboring atoms and consequently contain no dangling bond, thus resulting in no-undercutting at concave edges/corners.展开更多
文摘A combination of atomic force microscopy （AFM） and scanning electron microscopy （SEM） is used to characterize dislocation etch pits in Si-doped GaN epilayer etched by molten KOH. Three types of etch pits with different shapes and specific positions in the surface have been observed,and a model of the etching mechanism is proposed to explain their origins. The pure screw dislocation is easily etched along the steps that the dislocation terminates. Consequently a small Ga-polar plane is formed to prevent further vertical etching,resulting in an etch pit shaped like an inverted truncated hexagonal pyramid at the terminal chiasma of two surface steps. However, the pure edge dislocation is easily etched along the dislocation line,inducing an etch pit of inverted hexagonal pyramid aligned with the surface step. The polarity is found to play an important role in the etching process of GaN.
基金supported by the National Key Science & Technology Special Project (Grant No. 2008ZX01002-002)the Major Programand Key Program of National Natural Science Foundation of China (Grant Nos. 60890191 and 60736033)the Chinese Advance Research Program of Science and Technology (Grant Nos. 51308040301,51308030102,51311050112,and 51323030207)
文摘This paper reports that the yellow luminescence intensity of N-polar GaN Epi-layers is much lower than that of Ga-polar ones due to the inverse polarity, and reduces drastically in the N-polar unintentionally-doped GaN after etching in KOH solution. The ratio of yellow luminescence intensity to band-edge emission intensity decreases sharply with the etching time. The full width at half maximum of x-ray diffraction of （10-12） plane falls sharply after etching, and the surface morphology characterized by scanning electron microscope shows a rough surface that changes with the etching time. The mechanism for the generation of the yellow luminescence are explained in details.
文摘The etching characteristics of concave and convex corners formed in a microstructure by the intersection of {111} planes in wet anisotropic etchant are exactly opposite to each other. The convex corners are severely attacked by anisotropic Fetchant, while the concave corners remain unaffected. In this paper, we present a new model which explains the root cause of the initiation and advancement of undercutting phenomenon at convex corners and its absence at concave corners on {110} silicon wafers. This contrary etching characteristics of convex and concave corners is explained by utilizing the role of dangling bond in etching process and the etching behavior of the tangent plane at the convex corner. The silicon atoms at the convex edge/ridge belong to a high etch rate tangent plane as compared to {111} sidewalls, which leads to the initiation of undercutting at the convex corner. On the other hand, all the bonds of silicon atoms pertaining to concave edges/ridge are engaged with neighboring atoms and consequently contain no dangling bond, thus resulting in no-undercutting at concave edges/corners.
