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Tunnel diode
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<p>A tunnel diode or Esaki diode is a type of <a href="/facts/Semiconductor/zFf3mGTE">semiconductor</a> <a href="/facts/Diode/JyaoyGnk">diode</a> that has effectively "<a href="/facts/Negative_resistance/QgkR8esF">negative resistance</a>" due to the <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum mechanical</a> effect called <a href="/facts/Quantum_tunneling/WU4NMrKx">tunneling</a>. It was invented in August 1957 by <a href="/facts/Leo_Esaki/DP0IvTgb">Leo Esaki</a> and Yuriko Kurose when working at Tokyo Tsushin Kogyo, now known as <a href="/facts/Sony/7x4tCtBd">Sony</a>. In 1973, Esaki received the <a href="/facts/Nobel_Prize_in_Physics/o6w1nCbr">Nobel Prize in Physics</a> for experimental demonstration of the <a href="/facts/Electron_tunneling/WU4NMrKx">electron tunneling</a> effect in semiconductors. <a href="/facts/Robert_Noyce/J77WDDld">Robert Noyce</a> independently devised the idea of a tunnel diode while working for <a href="/facts/William_Shockley/wxlv4TcI">William Shockley</a>, but was discouraged from pursuing it. Tunnel diodes were first manufactured by Sony in 1957, followed by <a href="/facts/General_Electric/bBm5CzVY">General Electric</a> and other companies from about 1960, and are still made in low volume today. </p><p>Tunnel diodes have a heavily <a href="/facts/Doping_(semiconductor)/WrGdtWnm">doped</a> <a href="/facts/P%25E2%2580%2593n_junction/CaKIdLPg">positive-to-negative (P-N) junction</a> that is about 10 nm (100 <a href="/facts/%25C3%2585ngstr%25C3%25B6m/T5mjdd97">Å</a>) wide. The heavy doping results in a broken <a href="/facts/Band_gap/IjIeh95l">band gap</a>, where <a href="/facts/Conduction_band/2NUALlHJ">conduction band</a> <a href="/facts/Electron_configuration/TQjRr22P">electron states</a> on the N-side are more or less aligned with <a href="/facts/Valence_band/2NUALlHJ">valence band</a> <a href="/facts/Electron_hole/YymdTv9d">hole states</a> on the P-side. They are usually made from <a href="/facts/Germanium/wtoALHGs">germanium</a>, but can also be made from <a href="/facts/Gallium_arsenide/BakLFjpp">gallium arsenide</a>, gallium antimonide (GaSb) and <a href="/facts/Silicon/cgWx0hdr">silicon</a> materials. </p>