The authors observe resonant tunnelling of electrons and holes in a GaAs p-i-n diode incorporating two AlAs barriers in the undoped region. Peaks due to the HH1, LH1, E1 and HH2 (E=electron, LH=light hole, HH=heavy hole) resonances are observed, in that order of increasing voltage. The voltage separation of the LH1 and E1 resonance is significantly larger than expected from a simple quantum mechanical model due to an interaction effect involving resonant buildup of electron space charge in the quantum well. High magnetic fields B//J and B perpendicular to J are used to investigate the device and confirm the assignment of the resonances.