Heterojunction bipolar light-emitting transistors (HBLETs) fabricated with a lateral emission geometry for real-time optical wireless transmission

Heterojunction bipolar light-emitting transistors (HBLETs) with a cleaved facet in the lateral direction for light emission are proposed for real-time optical wireless transmission. To prevent light shielding by the top metal electrodes, the light output power of the edge-emitting HBLETs exceeds that of those emitting from the top surface. Although the proposed HBLETs can generate spontaneous light emissions at lambda similar to 965 nm, a reduced common-emitter current gain (beta similar to 0.41) was found due to some of the minority carriers (electron) from the emitter being radiatively recombined within the In0.15Ga0.85As/GaAs multiple-quantum-well containing base layer. Results also show that a 300 Mbit/s optical link can be constructed using the proposed HBLET transmitter with a lateral emission geometry but its modulation bandwidth is as high as 237.5 MHz. The paper also describes the use of HBLET-based optical wireless communications to achieve real-time transmissions of digital TV signals over a distance of 100 cm in free space.