A silicon, planar space-charge-limited current triode

Space-charge-limited currents (SCLC) of electrons and holes have been studied in P+NP+ and N+PN+ two terminal structures in both germanium and silicon (Shockley, Dacey, Ross, Shumka, Nicolet). When a third terminal has been applied to the "floating base" region of these structures operating under "punch-through" conditions, modulation of the SCLC was found to be very ineffective. Using epitaxial techniques, a multi-layer SCLC triode has been constructed with a high resistivity base layer between two high resistivity N layers to form a N+NPNN+ structure. Under space-charge-limited current operation one diode (source) is biased forward by the voltage across the entire structure. When a reverse bias is applied to this junction by a contact made to the P-layer (gate), effective modulation of the SCLC current is obtained. This reverse bias applied to the P-layer can thus be utilized as a high impedance gate-electrode.