A high-gain (Ga,Al)As/GaAs heterostructure bipolar transistor with an equilibrium-depleted spike-doped base

The fabrication is reported of a high-gain (Ga,Al)As/GaAs heterostructure bipolar transistor (HBT) with a p-spike-doped base that is depleted at equilibrium. The device structure, based on that proposed for a bipolar inversion-channel field-effect transistor (BICFET), was grown by molecular-beam epitaxy (MBE). Fabricated transistors, containing an AlAs/n-GaAs superlattice emitter layer, exhibited DC current gains of up to 500. Maximum current gains of tested devices occurred at collector current densities in the mid-10/sup 3/ A cm/sup -2/ range. It is postulated that the induced base in these transistors is formed predominantly by the forward-bias action on the base-emitter junction.<>