Electron-beam-induced reactivation of Si dopants in hydrogenated two-dimensional AlGaAsheterostructures: a possible new route for III–V nanostructure fabrication

Abstract

Hydrogen incorporation in n-type Si-doped GaAs epilayers is a well-known process whichleads to the neutralization of the active Si impurities with the formation of SiH complexes.Recently, we have shown that SiH complex dissociation and, consequently, Si-dopantreactivation could occur when the epilayers are exposed to an electron beam.Two epilayers have been studied: the first is a0.35 µm thick hydrogenated Si-doped GaAs epilayer and the second is Si planar-dopedAlGaAs/GaAs/InGaAs heterostructures.Firstly, Hall effect measurements have been carried out on the epilayers exposed, after RFhydrogen plasma exposition, to increasing electron doses with different injectionenergies. For the 2D heterostructures, we have observed that the free carrier densityNs does notvary significantly for weak electron densities. This reactivation presents a threshold value, contrary to the0.35 µm epilayerin which Ns varies quite linearly. It will be shown that such phenomena might be attributed to thefilling of surface states as the dopants are progressively reactivated.Then, using a high spatial resolution electron beam lithography system, nanometricconductive patterns have been fabricated starting from hydrogenated epilayers. Electricmeasurements have been performed and the results obtained show that about 15 nm spatialresolution could be expected.In conclusion, taking into account this spatial resolution, the high spatial contrast ofconductivity which could be expected due to the existence of an electron dosethreshold, and the high mobility of the AlGaAs/GaAs/InGaAs heterostructure,the effects described in this paper could open a new way for the fabrication ofIII–V 1D or 2D mesoscopic structures for electronic or optoelectronic applications.