A comparison of deep level defects in OMVPE GaAs layers grown on various GaAs substrate types

Abstract

In order to obtain epitaxial GaAs layers with a low enough defect concentration for an analysis of process induced impurities and defects, undoped OMVPE Layers were grown on different substrate types. Deep level transient spectroscopy (DLTS) showed that the epitaxial layers grown on all substrate types contained the EL2 electron trap in concentrations of about 1x1014/cm3. Apart from the EL2, layers grown on semi-insulating substrates, contained no electron traps in concentrations above 1011/cm3, while layers grown on most n+ and p+ substrates contained electron and hole traps in concentrations of well above 1013/cm3. It was therefore concluded that the choice of the proper substrate type when attempting to grow epitaxial layers with a low defect concentration is of the utmost importance.