硅基板和铜基板垂直结构GaN基LED变温变电流发光性能的研究

本文将硅(Si)衬底上外延生长的氮化镓(GaN)基发光二极管(LED)薄膜剥离转移到新的硅基板和紫铜基板上,并获得了垂直结构的LED芯片,对其变温变电流电致发光(EL)特性进行了研究. 结果表明:当环境温度不变时,在13 K低温状态下铜基板芯片的EL波长始终大于硅基板芯片约6 nm,在300 K 状态下随着驱动电流的加大铜基板芯片的EL波长会由大于硅基板芯片3 nm左右而逐渐变为与硅基板芯片重合;当驱动电流不变时,环境温度由13 K升高到320 K,两种基板芯片的EL波长随温度升高呈现S形变化并且波谱逐渐趋于重合;在100 K以下温度时铜基板芯片的Droop效应比硅基板芯片明显,在100 K 以上温度时硅基板芯片的Droop效应比铜基板芯片明显. 可能是由于两种芯片的基板具有不同的热膨胀系数和热导率导致了其变温变电流的EL特性不同.关键词：GaN热膨胀系数内量子效率热导率

Electroluminescence properties of vertical structure GaN based LED on silicon and copper submount at different temperatures and current densities

GaN-based light-emitting diode (LED) thin films grown on Si(111) substrates are successfully detached and transferred to copper and silicon submounts, and then become 40mil high power vertical structure LED chips. Electroluminescence properties of the two kinds of chips with the same expitaxial structure are investigated at different forward current densities and ambient temperatures. The obtained results are as follows. 1) at the same temperature, the EL peak wavelength of the chip with copper submount is longer than that of the chip with silicon submount. Under 13 K, the EL peak wavelength of the chip with copper submount is about 6 nm longer than that of chip with silicon submount as the driving current increases from 0.01 mA to 400 mA. While under 300 K, the difference in EL peak wavelength between the two kinds of chips at 0.01 mA is only about 3 nm; as the current increases to 400 mA, the difference will tend to zero and the spectra will coincide. 2) At the same current density, as the temperature increases from 13 K to 320 K, the EL peak wavelengths of the two kinds of chips are S-shaped, and the spectra tend to coincide. 3)When the temperature is below 100 K, the current density droop effect of the chips with copper submount is more abvious than that of chips with silicon submount, while above 100 K, the results are just inverse. Perhaps, it is due to the fact that the differences in thermal expansion coefficient and thermal conductivity between the two kinds of submounts lead to the diffrent EL properties.
Keywords：GaNthermal expansion coefficientinternal quantum efficiencythermal conductivity