Zn thin film on Al metal as thermal substrates for LED application: thermal and optical performance

摘要

Zn thin film at various thickness was deposited on Al substrates and used as thermal interface materials and tested their performance on affecting the thermal and optical properties of the LED at various driving currents. The total thermal resistance (R_(th-tot)) of the LED showed the influence of various thickness and annealing temperatures and observed low value for 300 nm and 400 nm at～150 °C. High difference in R_(th-tot) (△R_(th-tot) -3.78 KAV) was recorded with 300 nm Zn thin film annealed at 150 °C compared with bare Al substrates measured at 700 mA. Higher annealing temperature does not show much improvement on reducing the R_(th-tot) of the LED. Among the all Zn film studied, 300 nm thickness and annealed at 150 °C showed better performance on reducing the rise in junction temperatures (T_J) and the observed difference in T_J value was 8.07 °C compared with that of bare Al substrate measured at 700 mA. The optical output of LED was also supported the observed results and achieved improved light output for the same boundary conditions. High value in lux values was observed for the LED with 300 nm thickness and annealed at 150 °C and 350 °C for all driving currents. The roughness of Zn thin film increased with thickness and annealing temperature increased upto 500 nm and 350 °C respectively. The highest and lowest surface roughness of 112 nm and 21 nm were recorded for 500 nm and 800 nm thick Zn from 150 °C annealed samples respectively and supported the observation made by both thermal and optical analysis of the given LED. Overall, we may consider Zn thin film as solid thin film interface material for LED packaging application.