Growth of 6H-SiC homoepitaxy on substrates off-cut between the [01-10] planes
Vandersand Jr., James Dennis
The wide band-gap semiconductor silicon carbide has tremendous potential for use in high power, high temperature, and high frequency electronic devices. One of the more important design factors for these devices is the epitaxial layer. It is desirable that this thin film have uniform polytype, thickness, and impurity concentration, as well as be defect free. One method used for SiC to ensure epitaxial layers with homogenous polytype is to cut wafers from a boule that has been tilted towards a specific crystallographic face at a fixed angle (known as ?off cut?). The purpose of this thesis was to investigate the growth mechanisms of alternative boule tilting directions with 6H-SiC. Four alternative crystallographic tilting faces were chosen: <1230>, <1340>, <2130>, and <3140>. A lightly doped 1um-thick layer was grown on samples representing the four alternative off-cut directions and, as references, commercially available substrates off cut towards the traditional direction <1120>. The physical and electrical properties of the layers were characterized by means of optical microscopy, Fourier Transform Infrared Reflectance Spectroscopy, Atomic Force Microscopy, capacitance vs. voltage, and current vs. voltage. Three facts were observed: 1) the alternative off-cut directions affected the growth mechanisms and surface morphology, 2) the quality of the substrate affects the morphology of the epitaxy layer, and 3) the relative differences between the surface roughness attributed to the different off-cut directions affected the observed electrical characteristics of Schottky barrier diodes fabricated on the epi layers. The samples cut towards the <31-40> and <13-40> directions showed to the most promising alternative off-axis tilting direction.