The diameter of Czochralski (Cz) sapphire crystals is 50 mm. The sapphire substrates were lapped by using diamond powders and polished by chemical mechanical polishing(CMP) method using alkali slurry with SiO2 abrasiv...The diameter of Czochralski (Cz) sapphire crystals is 50 mm. The sapphire substrates were lapped by using diamond powders and polished by chemical mechanical polishing(CMP) method using alkali slurry with SiO2 abrasive. After obtaining the smooth surfaces, the chemical etching experiments were processed by using fused KOH and NaOH etchants at different temperature for different times. The dislocation was observed by means of optical microscope and scanning electron microscope. The clear and stable contrast images of sample etching pits were observed. On the whole, the dislocation density is about 104?105 cm?2. Comparing the results under the conditions of different etchants, temperatures and times during the etching proceeding, it was found that the optimal condition for dislocation displaying is etching 15 min with fused KOH at 290 ℃. At the same time, the formation of the etch pits and the reducing method of dislocation density were also discussed.展开更多
An ultraviolet (UV) laser lift-off (LLO) technique was presented to form a roughened surface morphol-ogy on GaN membrane grown by metalorganic chemical vapor deposition (MOCVD). The etched sur-face showed cone-like st...An ultraviolet (UV) laser lift-off (LLO) technique was presented to form a roughened surface morphol-ogy on GaN membrane grown by metalorganic chemical vapor deposition (MOCVD). The etched sur-face showed cone-like structures on a free-standing GaN membrane. Based on the scanning electron microscopy (SEM) and atom force microscopy (AFM) measurements, the etching mechanism was proposed, which was related to the different decomposition depth caused by the dislocations in the GaN membrane. The etching efficiency and morphology of GaN by the LLO technique and the photo-electrochemical (PEC) wet etching technique was compared and analyzed. This roughed cone-like surface morphology by LLO can enhance the external efficiency of vertical structure n-side-up GaN-based light-emitting diodes (LEDs) simultaneously while being released of the performance con-strains impeded by sapphire.展开更多
基金Project(59772037) supported by the National Natural Science Foundation of China project(500016) supported by the Hebei Natural Science Foundation Project(20050080007) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘The diameter of Czochralski (Cz) sapphire crystals is 50 mm. The sapphire substrates were lapped by using diamond powders and polished by chemical mechanical polishing(CMP) method using alkali slurry with SiO2 abrasive. After obtaining the smooth surfaces, the chemical etching experiments were processed by using fused KOH and NaOH etchants at different temperature for different times. The dislocation was observed by means of optical microscope and scanning electron microscope. The clear and stable contrast images of sample etching pits were observed. On the whole, the dislocation density is about 104?105 cm?2. Comparing the results under the conditions of different etchants, temperatures and times during the etching proceeding, it was found that the optimal condition for dislocation displaying is etching 15 min with fused KOH at 290 ℃. At the same time, the formation of the etch pits and the reducing method of dislocation density were also discussed.
基金Supported by the National High Technology Research and Development Program of China (Grant No. 2004AA311030)State Key Program of Basic Research of China (973) (Grant No. 20000683-02)+1 种基金Beijing Municipal Education Commission (Grant No. 2002kj018, Grant No. kz200510005003)Beijing Municipal Science and Technology Commission (Grant No. D0404003040221)
文摘An ultraviolet (UV) laser lift-off (LLO) technique was presented to form a roughened surface morphol-ogy on GaN membrane grown by metalorganic chemical vapor deposition (MOCVD). The etched sur-face showed cone-like structures on a free-standing GaN membrane. Based on the scanning electron microscopy (SEM) and atom force microscopy (AFM) measurements, the etching mechanism was proposed, which was related to the different decomposition depth caused by the dislocations in the GaN membrane. The etching efficiency and morphology of GaN by the LLO technique and the photo-electrochemical (PEC) wet etching technique was compared and analyzed. This roughed cone-like surface morphology by LLO can enhance the external efficiency of vertical structure n-side-up GaN-based light-emitting diodes (LEDs) simultaneously while being released of the performance con-strains impeded by sapphire.
