An Esaki diode (Leo Esaki, Nobel Prize 1973 for discovering the electron tunneling effect used in these diodes) or tunnel diode, has a heavily doped diode pn junction only some 100 Å wide. The heavy doping result in a broken bandgap, where conduction band electron states on the n-side are more or less alligned with valence band hole states on the p-side. Leo Esaki (江崎 玲於奈; correct transcription Esaki Reona; also known as Esaki Leona) (born March 12, 1925) is a Japanese physicist who won the Nobel Prize in Physics in 1973 for his discovery of the phenomenon of electron tunneling. ... In a conventional semiconductor diode, conduction takes place while the PN junction is forward biased, but the device blocks current flow when the junction is reverse biased. ... Ã…, or Ã¥, is a letter, representing a vowel, in the Swedish, Finnish, Danish, Norwegian, Walloon and Chamorro alphabets. ... In semiconductors and insulators, the conduction band is the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current. ... In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature. ...

Under normal forward bias operation, does electrons at first increasingly tunnel through the pn junction barrier when increasing voltage, because electron states in the conduction band on the n-side become increasingly alligned with valence band hole states on the p-side of the pn junction. As voltage increases further does these states become more misalligned again and the current drops - this is negative resistance, as current decreases with increasing voltage. As voltage increases yet further, does the diode begin to operate as a normal diode where electrons travel by conduction across the pn junction, and no longer by tunneling through the pn junction barrier. Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ...

Under reverse bias at sufficiently high reverse voltage, does electrons flow in the opposite direction, as now different electron states on each side of the pn junction become increasingly alligned and tunnel through the pn junction barrier in reverse direction - this is the Zener-effect used in zener diodes. Symbol of Zener diode. ...