Electron-hole bilayer light-emitting device: Concept and operation

We report a novel switched-mode light-emitting device (LED) in an undoped ultra-thin-body (UTB) based on the electrostatically-induced electron-hole bilayer (EHB) concept. The proposed device works on the principle of formation of EHB channels by applying suitable gate biases during the charging-cycle, and their recombination during a discharging-cycle. Using TCAD simulations, we show that continuous switching of the gates in an indium arsenide (InAs) based EHB LED with a ~12 μs time period leads to radiative recombination of the induced charge carriers with a peak internal quantum efficiency (IQE) as high as ~92% and a time-averaged IQE of ~29%. The proposed concept obviates the need for chemically doped p-n junctions in the UTB device for light-emitting applications. However, when relying on the thermal generation alone as a source of charge carriers in a small undoped semiconductor volume, a narrow bandgap semiconductor (such as InAs) is required for the proposed LED which ultimately limits the switching speed. For wider bandgap materials, highly doped regions on either side of the intrinsic UTB layer in the form of a lateral PIN structure could be employed where switching speed is then not limited by thermal generation. TCAD simulations of a silicon (Si) EHB LED based on such a gated PIN structure shows switching capability in the GHz frequency range making it attractive for SOI based optocoupling applications.