NOVELTY - Tunnel diode comprises a p-type (1101) device which is Positive Differential Resistor (PDR) or Negative Differential Resistor (NDR), and a n-type (1102) device which is NDR or PDR coupled with the p-type device, where either the p-type device or the n-type device is a PDR and the other device is a NDR, and the PDR and NDR are generated by thermal field, optical field, electric field, pressure field, and/or acoustic field.    USE - The tunnel diode is useful in a solar cell device, a light sensor, a Hall device, a thermal device, a pressure device, or an acoustic device (all claimed).    ADVANTAGE - The coupling PDR and NDR of the field tunnel diode can generate self-induced frequency elements which can modulate together to generate very broad frequency responses, which makes the field tunnel diode a broadband tunnel diode.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a transistor comprising: (a) a first device which is p-type or n-type and is PDR or NDR; (b) a second device which is p-type or n-type and is PDR or NDR coupled with the first device to form a first tunnel diode; and (c) a third device which is p-type or n-type and is PDR or NDR coupled with the second device to form a second tunnel diode, where the first, second, and third devices comprise a PDR and a NDR, and the PDR and NDR are generated by thermal field, optical field, electric field, pressure field, and/or acoustic field; and    (2) a capacitor comprising: (a) a first electrode having PDR property; (b) a second electrode having NDR property; and (c) a field-interacted dielectric disposed between the first and second electrodes and coupled with the first and second electrodes, where the field-interacted dielectric is interacted by thermal field, optical field, electric field, pressure field, or acoustic field, or any combinations of them for controlling the capacitance of the capacitor, and the PDR and NDR are generated by thermal field, optical field, electric field, pressure field, or acoustic field, or any combinations of them.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the tunnel diode.    P-type device (1101)    N-type device (1102)