Electrical Transport Properties of Metal-Insulator-Semiconductor (MIS) and Semiconductor-Insulator-Semiconductor (SIS) Structures

Abstract

<p>The major purpose of the work presented in this thesis has been to consider some important electrical transport properties of Metal-Insulator-Semiconductor (MIS or MOS) and Semiconductor-Insulator-Semiconductor (SIS) diodes.</p> <p>In particular the d.c. tunnel current-voltage characteristics of the MIS diode are studied and shown to divided naturally into two categories corresponding to the state of equilibrium of the semiconductor of a diode. In "equilibrium" diodes the carrier distributions in the semi-conductor are effectively maintained in thermal equilibrium despite the presence of d.c. current flow. I-V characteristics of a range of this type of diode are presented and analyzed. Tunnel induced non-equilibrium conditions in the semiconductor are also investigated and shown to have visible effects on the I-V characteristics of the MIS tunnel diode. These effects are seen to be functions of oxide thickness, minority carrier supply rate and doping density.</p> <p>The tunnel currents of both "equilibrium" and "non-equilibrium" diodes are analyzed by comparison with a comprehensive finite temperature tunnel theory. Employment of numerical techniques permits the inclusion in these calculations of the effects of a two band model of the insulator, image force potentials in the barrier and space charge tunneling.</p> <p>A practical application of the properties of the "non-equilibrium" diode in the form of a new type of active device, the Surface Oxide Transistor (SOT), is demonstrated. The characteristics of such structures are investigated and models of their operation proposed.</p> <p>The final work presented in this thesis deals with a new type of barrier dominated semiconductor structure, the SIS diode. The capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics of thick oxide diodes of this type are presented and compared with theory. A wide range of interesting characteristics are observed. The d.c. current-voltage behaviour of the SIS tunnel diode, while not studied experimentally, is compared qualitatively with that of the MIS tunnel diode.</p>