Investigation of LTPS and a-Si TFT pixel circuit for micro-light-emitting-triode with current gain

The driving capability of Micro-LED displays based on thin film transistor (TFT) often falls short due to limited TFT current output performance. In this study, we propose a 6T2C pixel circuit for micro light-emitting-triode (Micro-LET), which integrates GaN-based LED and bipolar junction transistor (BJT) in a single chip vertically. The proposed pixel circuit, utilizing low-temperature polysilicon (LTPS) TFT, effectively compensates for threshold voltage shifts and mobility variations, thereby addressing the issue of pixel non-uniformity. Circuit simulation results demonstrate that the current error rates (CER) of the emission current are less than 4.71 % and 1.83 %, respectively, when subjected to +0.5 V threshold voltage change and +30 % mobility variation. Furthermore, the LTPS TFT can be extended to amorphous silicon (a-Si) TFT in the pixel circuit, showcasing its potential in enabling high-brightness Micro-LED displays driven by a-Si TFT technology with current amplification capabilities. These findings validate the feasibility of cost-effective and highly luminous Micro-LED displays while also alleviating concerns regarding overcapacity issues associated with a-Si TFT.