in connection with the tunnel diode, when the doping concentrations on the p and n sides of a p-n junction are nearly or not quite very heavily doped with impurities, the current in the reverse direction for small bias is larger than the current in the forward direction. This is illustrated in Fig. 1. Due to the fact that the current in the reverse direction for small bias is larger than the current in the forward direction, it is known as backward diode. At thermal equilibrium, the Fermi level in the backward diode is very close to the band edges.
Under reverse bias, electrons can readily tunnel from the valence band into the conduction band and give rise to a teunneling current.
Advantages of Backaword Diode
. Similar to the tunnel diode, the backward diode has a good frequency response because there is no minority carries storage effect.
. V-I characteristics of backword diode is insensitive to temperature and to radiation effect.
. Backward diode has a very low noise.
. The ɣ is a measure of the degree of nonlinearity normalized to the operating admittance level. Ideally it should be greater than 40 V. For backword diode can exceed 40 V and unlike p-n junction diode or schottkey diode it is insensitive to temperature variation.
Applications
. Used for rectification of small signals.
. Used in microwave detection and mixing.
. Used in nonlinear applications such as high-speed switching.