3-DIMENSIONAL VERSUS 2-DIMENSIONAL ELECTRON-GAS INJECTION IN RESONANT-TUNNELING DEVICES

The nature of a small ''precursor'' of resonance which appears in fron t of the main resonance peak in the current-voltage characteristic of resonant-tunnelling devices based on GaAs/AlGaAs double-barrier hetero structures is studied. The competition between the precursor and main- peak current is examined within the temperature range 2-400 K and unde r a magnetic held up to 13 T. The precursor is interpreted as the cont ribution to resonant tunnelling of ballistic electrons injected from a three-dimensional electron gas in the emitter region. Instead, the ma in resonance peak is due to the electron injection from a two-dimensio nal electron gas in a triangular well formed under bias in the emitter spacer layer. (C) 1998 Elsevier Science B.V. All rights reserved.