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First-order Raman scatterings of hexagonal GaN layers deposited by the hydride vapour phase epitaxy and by metal-organic chemical vapour deposition on SiC and sapphire substrates are studied in a temperature range between 303 K and 503 K.The temperature dependences of two GaN Raman modes (A_1 (LO) and E_2 (high)) are obtained.We focus our attention on the temperature dependence of E_2 (high) mode and find that for different types of GaN epilayers their temperature dependences are somewhat different.We compare their differences and give them an explanation.The simplified formulas we obtained are in good accordance with experiment data.The results can be used to determine the temperature of a GaN sample.
First-order Raman scatterings of hexagonal GaN layers deposited by the hydride vapor phase epitaxy and by metal-organic chemical vapor deposition on SiC and sapphire substrates are studied in a temperature range between 303 K and 503 K. The temperature dependences of two GaN Raman modes (A_1 (LO) and E_2 (high)) are obtained. We focus on the temperature dependence of E_2 (high) mode and find that for different types of GaN epilayers whose temperature dependences are somewhat different. We compare their differences and give them an explanation. The simplified formulas we obtained are in good accordance with experiment data. The results can be used to determine the temperature of a GaN sample.