Hydrogen radical surface cleaning of GaAs for MBE regrowth (original) (raw)
Related papers
Thin Solid Films, 2002
An improved method to grow AlGaAsyGaAs structures on GaAs inside deep dielectric windows (DDWs) is reported. Samples which have undergone patterning and etching to form the DDWs were subjected to atomic hydrogen irradiation generated by a hydrogen cracker cell in a molecular beam epitaxy (MBE) system at a substrate temperature of approximately 450 8C and hydrogen background pressure of 10 torr. AlGaAsyGaAs quantum well structures of different well widths grown on GaAs y6 inside the DDWs pre-cleaned using atomic hydrogen showed two to five times improvement in photoluminescence (PL) linewidth compared to samples with area inside the DDWs subjected to thermal oxide desorption at 580 8C. The GaAs surface inside the DDWs cleaned using atomic hydrogen is atomically flat surface with surface roughness of 0.252 nm. This value is five times lower compared to that in the sample subjected to thermal oxide desorption. The use of atomic hydrogen is shown to be effective for cleaning the GaAs surface inside the DDWs, making it possible for MBE re-growth of high quality AlGaAsyGaAs structures for optoelectronic integration. ᮊ
Effect of the starting surface on the morphology of MBE-grown GaAs
Materials Science and Engineering: B, 2000
In this paper, we study the homoepitaxial growth of GaAs by molecular beam epitaxy on substrates that have different pre-growth roughness due to the method of removing the native oxide. The evolution of the surface roughness of 1 mm thick GaAs films grown at 553°C was monitored in real time using ultraviolet light scattering, and compared with ex situ atomic force microscopy measurements of the power spectral density (PSD) of the surface morphology. The PSD at a spatial frequency of 2 mm − 1 , is approximately three orders of magnitude larger for films grown on thermally cleaned substrates than for films grown on substrates cleaned with atomic hydrogen. No mounding indicative of unstable growth was observed in the films cleaned with atomic hydrogen.
High resolution photoemission yield study of the GaAs(100) surface cleaned by atomic hydrogen
2005
High-resolution photoemission yield spectroscopy (PYS) has been used to study the electronic properties of space charge layer of the real GaAs(100) surface cleaned by atomic hydrogen. The ionization energy, work function and interface Fermi level position were determined as a function of hydrogen dose. Moreover, the evolution of effective density of filled electronic states localized in the band gap and in the upper part of the valence band was observed. Our experiments showed that for the hydrogen dose up to 10 4 L H 2 the contamination etching stage occurs for which the interface Fermi level position E F-E v reaches a value of 1.06 eV. For the higher hydrogen dose at the level 10 5 L H 2 the interface Fermi level position E F-E v reaches a value of 0.75 eV which corresponds to the degradation of GaAs(100) surface that becomes covered by metallic Ga.
Selective area regrowth of n-GaAs with reduced interface carrier depletion using arsenic passivation
Journal of Crystal Growth, 1999
Selective area molecular beam epitaxy (MBE) of n-GaAs through a Si N mask has been explored. An arsenic capping layer was deposited in the MBE growth chamber prior to mask de"nition, in order to protect the epilayer surface during ex situ processing. After in situ thermal decapping and high-temperature (6803C) regrowth at a low growth rate (0.5 m/h), the samples were examined with scanning electron and atomic force microscopy. The data unveil selective regrowth with lateral de"nition on a micrometer length scale and GaAs surfaces with a smooth mirror-like "nish. Electrolytic carrier pro"ling and secondary ion mass spectrometry measurements of the homoepitaxial regrowth interface show a signi"cant reduction of the interface potential barrier, from < "0.45 V to < "0.07 V, and reduced carbon impurity concentrations, compared to regrowth on non-passivated GaAs epilayers.
H plasma cleaning and aSi passivation of GaAs for surface channel device applications
Journal of Applied Physics, 2009
We discuss GaAs͑001͒ cleaning and surface passivation for metal-oxide-semiconductor capacitors and field effect transistors fabricated with HfO 2 as high-gate oxide. An amorphous-Si passivating layer is deposited by molecular beam deposition on a 2 ϫ 1 reconstructed GaAs surface cleaned using a remote rf H plasma. The H plasma effectively removes C contaminants from the surface, but a progressive Ga enrichment and the presence of Ga-O bonds are observed. The capacitance-voltage measurements on capacitors under peripheral illumination show inversion, which is an indication of a passivated interface. The D it distribution as function of energy in the band gap is extracted by using the conductance technique at high and low temperatures and is reported for HfO 2 / a-Si gate stacks on H-cleaned GaAs. The observed D it distribution is asymmetric. Values as low as 7 ϫ 10 11 eV −1 cm −1 are found in the upper half of the band gap. One clear peak at 0.7 eV and a tail at 0.2 eV above the valence band maximum, which can be part of a second peak, are also observed. Transistor data confirm that a conducting channel is effectively opened at or very close to the GaAs surface.
Study of surface field in n-type GaAs before and after surface doping with H2
Applied Surface Science, 1992
Ap~,b~d S.r,~e '~ienc~ 5f, 5S (i,Jgz) gSt,-ghZ ' ]] [ Nnrth-tlolland surface Science Study of surface field in n-type GaAs bcfore and after surface doping with H.~ L, Kassel ', J.W. Garland, P.M. Raccah P.izy~)c~ Oclutrt~llt,nt, UJff~vrail)' of llliut~t~ ~lt ('ha'ago, i~ O. IJtzt 4348. ~Tnl'tlgo. IL 6Wi,~O. U.~I
Optical and electrical characterization of n-GaAs surfaces passivated by N< sub> 2–H< sub> 2 plasma
2003
The passivation of GaAs (1 0 0) surface has been performed by using remote N 2-H 2 (3% in H 2) RF plasma nitridation. The samples, consisting of n-doped GaAs wafers, show photoluminescence enhancement when the nitridation time and exposure to the plasma are in a narrow temporal window, so that a very thin (about 10 (A) GaN layer is deposited on the GaAs surface. Pure N 2 nitridation does not provide an efficient passivation, because it results in GaN layers with As and AsN x segregation at the GaN/GaAs interface. Increase of Au-GaAs Schottky barrier with the insertion of GaN interlayer and improvement of current-voltage characteristic have been observed.
Mechanisms for GaAs surface passivation by a molecular beam epitaxial cap layer grown at 200 °C
Journal of Applied Physics, 1992
A thin, undoped, molecular beam epitaxial (MBE) GaAs cap layer grown on top of an n-type conductive layer significantly reduces the free-electron depletion from the latter. By analyzing electron transfer to surface, interface, and bulk acceptor states in the cap, as a function of cap thickness, we show that either (1) the usual IQ-O.7 eV surface states are absent, (2) a dense donor near EC-O.4 eV exists or (3) a high donor interface charge (-5 X 101' cm-') is present. Any of these conclusions constitutes an important new aspect of low-temperature MBE GaAs.