The junction temperature of red,green and blue high power light emitting diodes(LEDs)is measured by using the emission peak shift method and the forward voltage method.Both the emission peak shift and the forward voltage decrease show a linear relationship relative to junction temperature.The linear coefficients of the red,green and blue LEDs for the peak shift method and the forward voltage method range from 0.03 to 0.15 nm/℃ and from 1.33 to 3.59 mV/℃,respectively.Compared with the forward voltage method,the peak shift method is almost independent of bias current and sample difference.The variation of the slopes is less than 2%for the peak shift method and larger than 30%for the forward voltage method,when the LEDs are driven by different bias currents.It is indicated that the peak shift method gives better stability than the forward voltage method under different LED working conditions.
A strain-compensated In P-based In Ga As/In Al As quantum cascade detector grown by solid source molecular beam epitaxy is demonstrated. The device operates at 4.3 m up to room temperature(300 K) with a responsivity of 1.27 m A/W and a Johnson noise limited detectivity of 1.02 107 cm Hz1=2/W. At 80 K, the responsivity and detectivity are 14.55 m A/W and 1.26 1010 cm Hz1=2/W, respectively. According to the response range, this detector is much suitable for greenhouse gas detection.
