The SIS tunnel emitter: A theory for emitters with thin interface layers

Abstract

Silicon n-p-n transistors are made with emitters consisting of a polycrystalline and monocrystalline region with a thin (20-60-Å) "insulating" interfacial layer in between (SIS structure). These transistors show a remarkable increase in emitter efficiency with emitter Gummel numbers up to 7 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> s.cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , and a low positive or even negative temperature coefficient of the current gain. A model is proposed to explain the mechanism in terms of tunneling through the interfacial layer. The electrical characteristics are measured in the temperature range 290-415 K. From the measurements it is deduced that the tunnel probability for holes (P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</inf> ) is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> and that for electrons (P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</inf> ) is >10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> . There also exists a band bending of 30-90 mV at the interfaces with the interfacial layer.