Technion Research & Development Foundation Ltd

Dan Ritter

Kurt Weiser

Nachum Shamir

Elia Zeldov

A heterojunction bipolar transistor (HBT) having an emitter structure capable of reducing the current crowding effect and preventing thermal instabilities is disclosed, wherein a negative differential resistance. (NDR) element is added to the layer structure of the conventional emitter. In accordance with the invention, the NDR element can be implemented, for example, by a Resonant Tunnel Diode (RTD) or an Esaki Diode structure. The NDR element is designed to limit the tunneling current to the maximal emitter current density required for safe transistor operation, thereby also reducing the current crowding effect.

High power bipolar transistor with emitter current density limiter

An optical apparatus and method for measuring the diffusion length in an insulating photoconductor or a semiconductor sample material, that includes a source of coherent light; means for splitting the light source and providing transmitted and reflected beams each having a variable light intensity, one of the transmitted and reflected beams being incident as a background beam at a location on the sample material, means for directing the other of the transmitted and reflected beams so as to be incident at the location as a probe beam, the directing apparatus establishing a predetermined angle between the background and probe beams at the location, polarizing means disposed in the path of the background beam and having one of two predetermined orientations corresponding to polarized and non-polarized states of the beam passing therethrough, means disposed in the path of the probe beam for periodically blocking the passage thereof; and means for measuring changes in the periodic photocurrent supplied by a power source through the sample material in response to the operation of the periodic blocking apparatus for each of the polarized and non-polarized states to thereby determine the diffusion length of the sample material.

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Haifa, Israel

Dan Ritter