Studies on the Effect of Temperature on Electroluminescence, Current–Voltage, and Carrier Lifetimes Characteristics in a InGaN/Sapphire Purple Light Emitting Diode

In this report, we have measured electroluminescence (El), current–voltage, and effective carrier lifetime characteristics in a InGaN/Sapphire purple light emitting diode (UV3TZ-395-15) in the temperature range from 350 K to 77 K. The semiconductor rate equations have been employed to analyse the light–current data to determine the relation of radiative efficiency (ηr) of the device with injection current at different temperatures, which is found to reach nearly 100% at 77 K with 20 mA current. The same analysis simultaneously leads to an evaluation of the non-radiative carrier lifetime (τnr) of the device and its temperature dependence. Next, using the data on voltage gradient obtained from the open circuit voltage decay (OCVD) process, as well as those of ideality factor from the current–voltage characteristics, measurement the variations of the effective carrier lifetime (τeff) with injection current at different temperatures have been evaluated. From the values of τnr and τeff , we have calculated the temperature dependence of the radiative lifetime (τr) of carriers. Using the values of lifetimes it is shown that the internal quantum efficiency (ηi) of the diode increases with lowering of temperature and reaches its maximum at about 120 K. Finally, this comprehensive study, apart from being highly useful in various optoelectronic applications, contributes to clarify our understanding of the physical processes at work in the device.