Intrinsic and extrinsic causes of electron accumulation layers on InAs surfaces

Using first-principles calculations we investigate the origins of electron accumulation on InAs surfaces. Among the possible intrinsic causes (i.e., involving only In and/or As), In adatoms are the only native defects that can induce a surface electron accumulation layer. As an extrinsic mechanism, we find that adsorption of hydrogen on the surface also leads to charge accumulation. Hydrogen is an ubiquitous impurity, present in all growth and processing environments and therefore likely to be present on InAs surfaces. Both indium and hydrogen adatoms create donor states above the InAs conduction-band minimum and can explain the observed electron accumulation.