Thermal transient measurements of high power GaN-based LEDs with multi-chip designs are presented and discussed. Once transient cooling curve was obtained, the structure function theory was applied to determine the thermal resistance of packages. The measured total thermal resistances from junction to ambient were 19.87 K/W, 10.78 K/W, 6.77 K/W for the one-chip, two-chip and four-chip package, respectively. The contribution of each component to the total thermal resistance of the package can be calculated from the cumulative structure function and differential structure function. The total thermal resistance of multi-chip package is found to decrease with the number of chips due to parallel heat dissipation. Very useful thermal design rule for high power multi-chip LED package is analogized from the experiments. It was found that the effect of the number of chips in a package on the thermal resistance depends on the ratio of partial thermal resistance of chip and that of slug. Thermal resistance for full color multi chip LEDs, where each chip is driven independently, was measured as well and the implication was discussed.

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CdTe films have been deposited onto HgCdTe by potentiostatic electrodeposition at deposition potentials of −0.4 V and −0.5 V with respect to a saturated calomel reference electrode in ethylene glycol base electrolyte. Films deposited with and without nitrogen bubbling to reduce dissolved oxygen in electrolytes were investigated by atomic force microscopy (AFM) and x-ray diffraction (XRD). Significant reduction in roughness (>1 orders) was observed by bubbling the electrolyte with 6 N nitrogen gas and the resulting films were highly oriented. The reduction in roughness is believed to be the result of the suppression of the reduction reaction whereby the dissolved molecular oxygen is converted to hydrogen peroxide and water that disturbs the ordered CdTe electrodeposition onto HgCdTe wafers.

A four-terminal gate-controlled diode structure has been used to characterize the surface recombination velocity of HgCdTe. The electrical performance of the gate-controlled diode fabricated using x=0.3 HgCdTe was characterized by capacitance-gate voltage and current-gate voltage measurements. A theoretical model was developed for the total dark current in the gate-controlled diode structure and used to fit the experimental data. Data fitting when the experimental device was operated in depletion mode allowed the simultaneous extraction of the surface recombination velocity, 170 cm/s, the generation lifetime in the n-p junction depletion region, 12 ns, and the generation lifetime in the gate induced junction depletion region, 500 ns.

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