A novel hot electron light-emitting device is proposed which operates by the application of longitudinal electric field, i.e. in the plane of the GaAs quantum wells, which are placed next to the junction plane of an (\mathrm{n}-\mathrm{Ga}{1-\mathrm{x}} \mathrm{Al}{\mathrm{x}} \mathrm{As}-\mathrm{p}) - (\mathrm{GaAs}) heterostructure. Application of high electric fields results in the transfer of hot electrons via tunnelling and thermionic emission, from the quantum well in the depletion region, into the GaAs inversion layer. The hot holes in the p-GaAs, initially away from the junction, then diffuse towards the junction plane to recombine with the excess hot electrons, giving rise to electroluminescence (EL) which is representative of the GaAs band-to-band emission. As the applied field is increased, a highenergy tail in the EL spectrum develops, and, photons with energies greater than the el-hhl transition energy in the quantum well are absorbed and re-emitted by the quantum well. Thus a second peak develops in the EL spectra which becomes stronger with increasing applied electric field. The device has been theoretically modelled, by solving Schrodinger and Poisson's equations self-consistently, to understand the processes leading to EL emission in the various channels.