Methods of electrically characterizing zinc selenide epitaxial layers on gallium arsenide substrates

A number of different methods for electrically characterizing ZnSe thin films are presented. These include the Hall effect, current-voltage profiling, and capacitance-voltage profiling. The planar Schottky technique is used to analyze p-type ZnSe. The conductance method of Nicollian and Brews is applied for the first time to the ZnSe/GaAs MIS system to find the surface state density profile and the time constants associated with particular states. A novel photowash technique is used to make the GaAs surface gallium rich before ZnSe growth. Electron Paramagnetic Resonance is discussed in the context of probing thin film semiconductors.\nRoom temperature mobilities for undoped, 1 $\\rm\\mu m,$ ZnSe films grown by Laser-assisted Metal Organic Chemical Vapor Deposition are as high as 309 $\\rm cm\\sp2/V$-s. Measured mobilities at 77 K are low due to hole conduction in p-type GaAs at the interface. Heterojunction barrier heights are found to be in the range of 0.6-0.9 eV and are most likely due to interface traps. Schottky diode n-values are found to be high ($>$30) because of the heterojunction barrier. P-type conduction in the nitrogen-doped samples has not been found. Undoped ZnSe is n-type and is typically depleted of carriers. Surface state densities for both untreated and Ga-rich ZnSe/p-GaAs interfaces are found to be in the range of $10\\sp{12}$ $\\rm cm\\sp{-2}$-$\\rm eV\\sp{-1}.$