Electroluminescence from the base of a GaAs/AlGaAs double heterojunction bipolar transistor.

We have measured the electroluminescence spectrum of a double heterojunction bipolar transistor and found that a potential well formed at the base-collector junction acts as a preferential trap of low energy electrons in the base. At high injection current densities the trap saturates with the subsequent build up of carriers in the base changing the transistor turn-on characteristics.