Abstract
This thesis is concerned with the formation, assessment, and application of surface layers in a semiconductor, A surface layer is defined to be a layer substantially the whole of which controls the potential distribution and electric field at the surface of a semiconductor, As such, it is very shallow, typically 100A deep. Two methods of doping surface layers are considered, firstly direct implantation of impurities at low energies and secondly recoil implantation of impurities from a thin film. The profiles arising from these two approaches are predicted particularly for the preferred system of antimony in silicon. Assessment techniques based on the metal-semiconductor (Schottky) barrier are developed with the aim of relating the total current passing through a Schottky barrier to the total electrical activity in a surface layer. This is shown to be a particularly powerful technique when the distribution of impurities is symmetrical about a point below the surface. Electrical assessment of surface layers formed by direct implantation of antimony at energies in the range 5-15keV are reported as well as results on layers formed by recoil implantation from an antimony film using either krypton or neon bombardment. Rutherford backscattering measurements are used to monitor such things as recoil yield and inert gas retention and using backscattering at 'glancing incidence' to increase the depth resolution, relevant features of directly implanted surface layers are obtained. Having formed surface layers they are then applied to the Schottky barrier system. It is shown that using surface layers to control the sign and magnitude of the surface field, the effective barrier height of a Schottky diode can be controlled over a wide range and considerable flexibility is brought to the system. This can be done without major degradation of any other characteristic of the diode. The unique situation which arises using implanted surface layers enables one to obtain basic information about current transport in the Schottky barrier vital to the assessment techniques mentioned above. In particular, an estimate is made of the tunnelling effective mass in the direction in silicon.