A Comparison of Low-Energy As Ion Implantation and Impurity-Free Disordering Induced Defects in N-Type GaAs Epitaxial Layers (original) (raw)
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Ion implantation and low‐temperature epitaxial regrowth of GaAs
Journal of Applied Physics, 1981
Channeling and transmission electron microscopy have been used to investigate the parameters that govern the extent of damage in ion-implanted GaAs and the crystal quality following capless furnace annealing at low temperature (-400 •q. The implantation-induced disorder showed a strong dependence on the implanted ion mass and on the substrate temperature during implantation. When the implantation produced a fully amorphous surface layer the main parameter governing the regrowth was the amorphous thickness. Formation of microtwins after annealing was observed when the initial amorphous layer was thicker than 400 A. Also, the number of extended residual defects after annealing increased linearly with the initial amorphous thickness and extrapolation of that curve predicts good regrowth of very thin (< 400 A) GaAs amorphous layers produced by ion implantation. A model is presented to explain the observed features of the low-temperature annealing of GaAs.
Damage production in GaAs during MeV ion implantation
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1996
The influence of the nuclear and electronic energy loss on the damage production in GaAs has been studied by Se+ ion implantation at Ti = 293 K with energies ranging from 2 MeV up to 20 MeV. The ion dose was varied between 5 X 10i2/cm2 and 1 X 10'5/cm2. The damage production was investigated using RBS in channeling regime. Temperature and energy dependent backscattering measurements and TEM investigations were performed to study the kind of defects in more detail. The resulting defect profiles are compared with the depth distribution of the nuclear and electronic energy loss which were simulated by TRIM 87. The results show that the remaining defect concentration strongly decreases with increasing implantation energy even if the same energy density is deposited into nuclear processes. We suppose, that the electronic energy loss increases the defect transformation and annealing during implantation at T, = 293 K. The defects in the samples implanted with energies greater than 5 MeV are characterized as point defects, point defect clusters and small dislocation loops; the kind of defects are the same over the whole implantation depth and the existence of amorphous zones can be widely excluded.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2003
The effect of stress on defect creation and diffusion during impurity-free disordering of SiOx-capped n-GaAs epitaxial layers has been investigated using deep level transient spectroscopy. The oxygen content in the SiOx layer and the nature of the stress that it imposes on the GaAs layer were varied by changing the nitrous oxide flow rate, N, during plasma-enhanced chemical vapor deposition of the capping layer. The peak intensity of defects S1 and S4 increased with the increasing nitrous oxide flow rate to exhibit a maximum in the range 80 sccm<N<200 sccm. Any further increase in N resulted in a decrease in peak defect intensity, which reached an almost constant value for N>350 sccm. On the other hand, the peak intensity of S2* increased linearly with N. We have explained the maximum in the intensity of defects S1 and S4 for 80 sccm<N<200 sccm to be due to a corresponding maximum in the compressive stress which is experienced by the capped GaAs layer during annealing...
Defect Engineering and Atomic Relocation Processes in Impurity-Free Disordered GaAs and AIGaAs
2004
Impurity-free disordering (IFD) of GaAs and Al x Ga 1-x As epitaxial layers using SiOx capping in conjunction with annealing was studied by deep level transient spectroscopy (DLTS) and capacitance-voltage (C-V) measurements. Three dominant electron traps S1 (E C-0.23 eV), S2 * (E C-0.53 eV), and S4 (E C-0.74 eV) are created in disordered n-type GaAs. The electron emission rate of S1 is enhanced in the presence of an externally applied electric field. We propose that S1 is a defect that may involve As-clustering or a complex of arsenic interstitials, As i , and the arsenic-antisite, As Ga. S2 * is shown to be the superposition of two defects, which may be V Ga-related. S4 is identified as the defect EL2. Our preliminary results indicate that the same set of defects is created in disordered n-type Al x Ga 1-x As, with S1 pinned to the conduction band edge, while S2 * and S4 are pinned relative to the Fermi level. In contrast to disordering in n-type GaAs, IFD of p-type GaAs results in the pronounced increase in the free carrier concentration in the near-surface region of the disordered layer. Two electrically active defects HA (E V + 0.39 eV) and HB2 (E V + 0.54 eV), which we have attributed to Cu-and As i /As Garelated levels, respectively, are also observed in the disordered p-GaAs layers. IFD causes segregation of Zn dopant atoms and Cu towards the surface of IFD samples. This atomic relocation process poses serious limitations regarding the application of IFD to the band gap engineering of doped GaAs-based heterostructures.