Doping of GaAs epitaxial layers grown on (100) GaAs by close-spaced vapor transport

Abstract

Using H2O as a transport agent, epitaxial GaAs layers were grown by the close-spaeed vapor transport technique (CSVT) on (100) heavily Si-doped GaAs substrates. Three kinds of GaAs sources were used for the deposition: (100) GaAs, heavily doped with Te or Si, and undoped semi-insulating (SI) (100) GaAs. The growth rates obtained with SI and Te-doped GaAs are quite similar and show a clear tendency to be superior to the growth rates measured for Si-doped GaAs sources. Uncompensated charge carrier density (ND – NA) profiles have been measured electrochemically for the layers grown with the three kinds of sources. When Te-doped GaAs is used, (ND – NA) obtained for the epitaxy is the same as that of the source, implying a complete transfer of the Te impurity. (ND – NA) values varying from 1016 to 1018 cm−3 are obtained from SI GaAs sources, depending upon the thickness of the epitaxial layer. (ND – NA) < 1015 cm−3 are measured for layers grown from Si-doped GaAs sources. In this case, layers thicker than 10 μm cannot be mesured electrochemically because of their excessively high resistance. The small (ND – NA) values obtained in that case are explained by the reaction of Si contained in the source with the transport agent (H2O), resulting in the formation, at the Si-doped GaAs surface, of a passivating SiOx layer revealed by Auger spectroscopy. This passivating layer also explains the smaller growth rates measured with these sources. p–n Junctions have been prepared by Zn diffusion in CSVT layers grown from SI GaAs sources. Their I–V characteristics show good rectification behavior, indicating that the CSVT layers could be used for photovoltaic purposes.

Doping and electronic properties of GaAs grown by close-spaced vapor transport from powder sources for scalable III–V photovoltaics

“…It has been shown using impedance proling that GaAs lms grown using CSVT from Te-doped wafers possess N D equivalent to the source wafers. [43][44][45] We reproduced these results by using two n-GaAs:Te sources with different [Te] to grow GaAs lms on degenerately-doped GaAs:Si substrates and measuring N D with impedance proling. In order to conrm that the dopants were transported by CSVT and not diffused from the substrate, we also deposited n-GaAs:Te lms on undoped, semi-insulating substrates.…”

Growth by the CSVT (close-spaced vapor transport) technique and characterization of epitaxial GaAs layers on Ge substrates

“…The close-spaced system has already been described elsewhre (6). The graphite blocks (5 x 4 x 0.5 cm3) heating the source and the substrate limit the maximum dimension of the Ge substrates to 1 % in in diameter (8 cm') but the system could easily be scaled up.…”

“…Both {400), the most diffracting planes in (100) GaAs or Ge, and (200) planes, diffracting only in GaAs, have a too low multiplicity (6). These poles are situated in the center of the pole figure and along its perimeter being therefore inaccessible to a measurement reaching + = 88".…”

“…Some doping impurities, however do not react easily with H,O but are able to sublime and are transported in the elemental form (6,7). Switching from one impurity to another is less easy in CSVT than in chemical vapour deposition (CVD) because it requires a change of the source.…”

Evidence Provided by SIMS and EXAFS, of Ge Microclusters in GaAs Epitaxial Layers Obtained on Ge by CSVT

“…The raw SOI substrates have been evaluated by ellipsometry (3, 4), spreading resistance (5), four-point probing (6), low-temperature transport (7,8), Hall effect spectroscopy (9), and photo-induced current transient spectroscopy (PICTS) The raw SOI substrates have been evaluated by ellipsometry (3, 4), spreading resistance (5), four-point probing (6), low-temperature transport (7,8), Hall effect spectroscopy (9), and photo-induced current transient spectroscopy (PICTS)…”