1. A multi-well diode, for use with various external devices, comprising: (a) a cathode comprising a doped semiconductor material, said cathode having a first boundary and a second boundary, said first boundary being electrically connected to one of said external devices; (b) a multi-well region, comprising: (i) at least one barrier comprising semiconductor material exhibiting a wider energy band gap than the energy band gap of said cathode, said at least one barrier having a first boundary and a second boundary, the first boundary of the first of said at least one barrier forming an electrical junction with the second boundary of said cathode; (ii) at least one deep well comprising doped semiconductor material exhibiting a narrower energy band gap than the energy band gap of said at least one barrier, said deep well having a first boundary and a second boundary, the first boundary of said at least one deep well forming an electrical junction with the second boundary of said at least one barrier; (iii) an end barrier comprising semiconductor material exhibiting a wider energy band gap than the energy band gap of said at least one deep well, said end barrier having a first boundary and a second boundary, the first boundary of said end barrier forming an electrical junction with the second boundary of the last of said at least one deep well; and (c) an anode comprising a doped semiconductor material exhibiting a narrower energy band gap than the energy band gap of said end barrier, said anode having a first boundary and a second boundary, the first boundary of said anode forming an electrical junction with the second boundary of said end barrier, and said second boundary of said anode being electrically connected to one of said external devices; wherein said multi-well diode operates in a low conductance state at forward bias until said multi-well diode's threshold voltage is exceeded, at which time said multi-well diode briefly operates in an unstable negative resistance region as it switches into a high conductance state, after which said multi-well diode remains in the high conductance state until the forward voltage across and current through said multi-well diode decreases below the multi-well diode's holding condition, at which time said multi-well diode switches back into the low conductance state, thereby exhibiting an S-curve current-voltage characteristic in forward bias.