Correlation of surface properties with electron emission characteristics for wide bandgap semiconductors

This study explores the electron emission characteristics of 6H-SiC and the III-Nitrides, including AlN and GaN. The effect of morphological differences on the field emission properties of GaN is determined. Arrays of silicon doped GaN pyramids yields an enhancement of the electron emission properties over that of flat films. Both GaN and 6H-SiC can be readily doped n-type. The electron affinity of GaN and 6H-SiC has been determined to be between 3 eV and 4 eV. This means that these materials have low work functions and possibly a low surface barrier to electron emission. The addition of adsorbates to the surface of 6H-SiC has been explored. A hydrogen plasma treatment at the surface of 6H-SiC has been shown to increase the electron affinity. The effects of this increase in the electron affinity to the threshold field for electron emission is studied. The presence of a negative electron affinity on AlN thin films grown on alpha(6H)-SiC(0001) has been reported. However, to date, attempts to dope AlN n-type have failed. Field emission measurements of AlN thin films yield high threshold fields and damage from vacuum micro-arcs to the sample. The addition of titanium to the surface of AlN results in an interface dipole of 1.5 +/- 0.2 eV. The resulting dipole that is formed causes an increase in the surface barrier to electron emission.