The realization of collector‐up light‐emitting complementary charge injection transistors is reported. The devices have been implemented in molecular‐beam‐epitaxy‐grownn‐InGaAs/InAlAs/p‐InGaAs andn‐InGaAs/InP/p‐InGaAs heterostructures using a self‐aligned process for the collector stripe definition. Electrons, injected over the wide‐gap heterostructure barrier (InAlAs or InP) by the real‐space transfer (RST) process, luminesce in the low‐dopedp‐type InGaAs active layer. An essential feature of present devices, besides their self‐aligned collector‐up configuration, is a relatively heavy doping of then‐type emitter channel, with the sheet dopant concentration of 4×1012cm−2. This ensures a higher uniformity of the electric field in the channel and provides a relief from RST instabilities at a high level of collector current (linear density ∼10 A/cm). Devices with InAlAs and InP barriers show rather different optical characteristics, mainly due to the different band lineups &Dgr;EC/&Dgr;EVin InGaAs/InAlAs and InGaAs/InP heterostructures, leading to different ratios between the RST current and the parasitic leakage of holes from the collector into the channel. At high RST current densities, the effective carrier temperatureTein the active collector layer, determined from the high‐energy tails of the luminescence spectra, is strongly enhanced compared to the lattice temperature. This decreases the device radiative efficiency and leads to a thermionic emission of carriers out of the active layer.