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The Reason for the Production of Junction Temperature

The basic structure of LED is a semiconductor, P – N junction. The experiment points out that P – N junction temperature will rise when the current go through the LED components, technically, we usually define the P – N junction zone temperature as the LED junction temperature. Usually, we put the temperature of LED chip as junction temperature because circuit chips have very small size. When working in the LED, the LED junction temperature will rise at different level in the following five circumstance: 1.Bad element electrode structure, window substrate structure or the materials and conductive silver glue have certain resistance, the resistance overlay on each other and constitute the series resistance of LED components. When current flows through the P – N junction, it also flows through the resistor, resulting in a joule heat, and give rise to junction temperature or the temperature chip. 2.Because the P – N junction can’t extremely perfect, the component injection efficiency does not reach 100%, which means, when the LED workes, not only P area inject electrons to N area(hole), but also N area inject electrons to P area (electronic). Under normal circumstances, in the later injection, it won’t produce photoelectric effect but consumed in the form of heat. Even if the useful part of the injection, it also won’t all become light, some of it combinate with defects or precipitates in junction area and eventually become hot. 3. Practices has proved, the light efficiency limit is the main cause of the LED junction temperature rise high. At present, the advanced material and device manufacturing technique have made it possible for LED to make the most input energy converted to optical radiant energe, however, compared LED chip material to the surrounding media, LED chip material has a much larger refractive index which cause the great part of the photon in the chip.

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