Development of Heterojunction c-Si/a-Si_1-xC_x:H PIN Light-Emitting Diodes

In this work, we explored the feasibility of the fabrication of PIN light-emitting diodes (LEDs) consisting of heterojunctions of amorphous silicon-carbide (a-Si_1-xC_x:H) thin films and crystalline silicon wafers (c-Si). The objective is the future development of electro-photonic systems in the same c-Si wafer, containing transistors, sensors, LEDs and waveguides. Two different heterojunction LEDs were fabricated consisting of PIN and PIN⁺N structures, where a-Si_1-xC_x:H thin films were used as P-type and I-type layers, while an N-type c-Si substrate was used as an active part of the device. The amorphous layers were deposited by the plasma-enhanced chemical vapor deposition (PECVD) technique at a substrate temperature of 200 °C. The PIN device presented electroluminescence (EL) only in the forward bias, while the PIN⁺N device presented in both the forward and reverse biases. The EL in reverse bias was possible due to the addition of an N⁺-type a-Si:H layer between the c-Si substrate and the I-type a-Si_1-xC_x:H active layer. Likewise, the EL intensity of the PIN⁺N structure was higher than that of the PIN device in forward bias, indicating that the addition of the N-type a-Si:H layer makes electrons flow more efficiently to the I layer. In addition, both devices presented red EL in the full area, which is observed with the naked eye.