Si衬底GaN基LED的结温特性

结温是发光二极管的重要参数之一,它对器件的内量子效率、输出功率、可靠性及LED的其他一些性能有很大的影响。首次报道Si衬底GaN基LED的结温特性。利用正向压降法测量Si衬底上GaN基LED的结温,通过与蓝宝石衬底上GaNLED的结温比较,发现Si衬底GaNLED有更低的结温,原因归结为Si有更好的导热性。同时也表明:用Si作GaNLED的衬底在大功率LED方面具有更大的应用潜力。

The Junction-temperature Characteristic of GaN Light-emitting Diodes on Si Substrate

The development of some applications on silicon(Si) substrates has obvious technological advan-(tages),including the low cost,large-scale availability,good thermal and electrical conductivities and the feasibility of removing the Si substrates with wet etching.Significant mismatches in lattice constants and thermal expansion coefficients of silicon and GaN in growth process is encounted,such differences cause crack formation when the thickness of the grown film exceeds a critical thickness.Recently,considerable developments in this field has been achieved,GaN LED grown successfully on Si was reported.Junction temperature is a key parameter of light emitting diode(LED),the junction temperature characteristic of GaN LED on Si substrate is reported firstly.The junction temperature of GaN on Si was measured under forward voltage.This method is based on the dependence of junction temperature on operating voltage.This relationship can be measured and used to compute the semiconductor junction temperatures in response to power dissipation in the junction region.This measurement consists of two steps of measuring: the calibration measurement and the actual junction-temperature measurement.The results showed that the junction temperature of GaN LEDs on Si substrate is different from that on sapphire substrates.The junction temperature on Si substrate is lower than that on sapphire,and the increase speed of the junction temperature is lower on Si substrate than that on sapphire substrate,especially in high operating current.We believe that this phenomena results from the better thermal conductivity of Si substrate than sapphire substrate(the thermal conductivity for Si and sapphire are 5 W/cm·K and 1.5 W/cm·K,respectively).The result that junction temperature is still low in high current suggests that the GaN-base LEDs on Si substrate have much more potential for the application on the high power devices.