Characterization of cylindrical and conical like zinc oxide light emitting diode structures

Unlike the traditional lighting system, the usage of light emitting diode (LED) lighting technology be able to sustain the economy growth due to drastically drop in power usage, be able to prevent harmful occurrences to the user due to the production of heat by electricity waste, and also be able to reduce the greenhouse effect. In contrast with the conventional lighting system, LED’s technology possesses a characteristic of an environmental friendly lighting system. In this work, zinc oxide (ZnO) is used as the main material of LED’s chip. This is because of ZnO not only low-in-cost but also readily available in the current market. Therefore, the initial cost of LED can be reduced and lowered compare to the existing LEDs. The main purpose of this study is to investigate the effect of doping layer thickness as well as the bias voltage in cylindrical and conical-like LED chips structure. All results are recorded and compared in terms of current-voltage (I-V) characteristic, emission rate and internal quantum efficiency (IQE). Both geometrical structures, cylindrical and conical like, hold an equivalent diameter and thickness which is 50µm and 10µm respectively. Besides, the bottom edge of cylindrical and conical-like structures is attached with a ring of n contact. The metal ring is composed of 5µm of width and 2µm of thickness, making the bottom diameter for the cylindrical and conical-like structure 60µm. Meanwhile, the p contact is designated at the top of the structures, creating a metal disk. The doping layer thickness is varied from 1µm of p-type layer with 9µm of n-type layer thickness. This layer is further diverted until it reaches 9µm of p-type with 1µm of n-type thickness. A fixed value of driven voltage is maintained at 6V. As a result, the cylindrical dimension shows a higher turn-on voltage and a higher percentage of IQE compares to the conical like structure. In addition, the percentage of IQE for both structures is also increased as the p-type layer thickness is enhanced. The conical-like structure demonstrates more favorable results of emission rate than the cylindrical shape of LED chip. Therefore, the conical-like chip is able to produce a brighter emission of light. The research is then preceded by varying the amount of voltage supply. A constant value of doping layer thickness is adopted which is 5µm for p-type and n-type layers. Based on the obtained results from I-V curve, the entire category illustrates a similar value of turn-on voltage which is 1V. Other than that, both of cylindrical and conical like structures indicate a better result of emission rate when a higher voltage is supplied through the p-n junction. The conical-like structure possesses lower percentages of IQE in comparison to the cylindrical dimension. The percentage also decreases as the voltage supply is increased for both geometrical structures. Since the performance of LED is greatly related to the brightness, the conical-like dimension is a better structure for LED chip.