Direct determination of electron capture in QWIPs

We present a method for measuring the capture probability, p(c), of excited electrons into quantum wells. Using this method p(c) is determined directly as a function of electron energy above the well. The base and emitter currents are measured in an HBT-like structure with the quantum well as a bass. The capture probability, given by the ratio between these currents, is determined as a function of junction bias. The capture mechanisms are probably due to electron - hole and electron - hole-plasmon interactions in the p' type well. The probability remains high even for "hot" electrons, being about 50% for electrons injected with energy as large as 500 meV above the well.