For the research of next-generation displays, technology of shrink device size is the most attractive and important technology. It is possible to manufacture high-performance display products by using high integrated devices such as mobile application. However, there is a certain limitation to the downsizing technology. Therefore, new device synthesis techniques are becoming important. In this paper, we propose a device design that combines inorganic material based light-emitting diode (LED) and thin-film transistor (TFT). By integrating the LED and TFT devices into one region, it is possible to highly integrate the devices, which can greatly reduce the size of the entire device. To investigate a possibility of device implementation, technology computer-aided design (TCAD) simulation is used. After that, an optical and electrical characteristic of the device are analyzed. Finally, the light-emitting transistor (LET) is proposed.