Microstructural evolution of a recrystallized Fe-implanted InGaAsP/InP heterostructure

Abstract

Through the recrystallization of an amorphous heterostructure, obtained by MeV Fe ion implantation, we are able to tailor a standard epitaxial semiconductor material, a small gap InGaAsP/InP alloy, for photoconductive terahertz optoelectronics. Here, we report on microstructural changes occurring in the material over a broad range of rapid thermal annealing temperatures, using X‐ray diffraction line profile analysis and transmission electron microscopy. Results show a complete amorphous transition of the heterostructure after multiple‐energy implantations done at 83 K. Upon thermal annealing, multiple structural layers develop via solid phase epitaxy and solid phase recrystallization. The photoconductive InGaAsP layer becomes polycrystalline and submicron grained, with high crystalline volume fraction and apparent ⟨110⟩ texture. Many grains are elongated and internally faulted, with high densities of planar faults occurring on closed‐packed (111) planes. The X‐ray diffraction line broadening is anisotropic and evolves with rapid thermal annealing temperatures. At 500 °C, the X‐ray coherent domain size estimate of 10 nm is aligned reasonably with electron microscopy made in faulted areas. Above 500 °C, a significant decrease of the planar fault density is detected. We discuss the influence of these microstructural changes happening with recrystallization temperatures on the ultrafast photoconductive response of Fe‐implanted InGaAsP/InP.

Critical process temperatures for resistive InGaAsP/InP heterostructures heavily implanted by Fe or Ga ions

“…5(b) and (d), which implies the transformation of the amorphous structure into a polycrystalline structure due to recrystallization occurring during RTA. A polycrystalline structure was detected in all quaternary materials that were Fe-or Ga-implanted at T impl = 83 K and 300 K. These microstructures have been investigated by XRD line profile analysis and electron microscopy, and details are published elsewhere [18]. For Fe-implanted 1.57Q at 83 K, our findings confirm the full amorphization of the InGaAsP/InP structure up to 1.9 lm below the sample surface.…”

“…7 shows that above 400°C cold Fe implantation can produce higher sheet resistivity and lower sheet carrier densities than cold Ga implantation. This suggests a non-negligible contribution to carrier compensation from Fe within at least one of the defective InGaAsP or InP structural layers of the recrystallized heterostructure [18]. However, this contribution occurs at RTA temperatures much lower than those found, and known to be related to Fe activation, using lower, non-amorphizing, Fe implantation fluences in In 0.57 Ga0 .47 As [24].…”

Ultrafast photocarrier dynamics in Fe-implanted InGaAs polycrystalline photoconductive materials

“…The films were grown at 450 • C with trimethylindium (TMIn), triethylgallium (TEGa) and cracked arsine (AsH3) as precursors. The asgrown film was implanted with Fe ions at 83 K following a multi-energy scheme to amorphize the crystalline film and to increase its resistivity [11,13]. The Fe ions were irradiated at a 7 • angle to the surface of the film at five energies 0.35, 0.65, 1.8, 2.08 and 3.54 MeV with doses of 0.75, 1.2, 2.35, 3.15 and 5 × 10 14 cm −2 , respectively.…”

“…An average concentration of 2.3 × 10 20 cm −2 Fe ions over the entire thickness of the InGaAs layer is obtained by summing all the implantation profiles. At such high doses, the InGaAs film is completely amorphized [11][12][13]. The ion-implanted films were then processed by RTA at five different temperatures: 300, 400, 500, 600 and 700 • C. The thermal annealing was performed under nitrogen atmosphere using GaAs proximity capping to prevent As desorption from the sample surface during annealing.…”

“…These findings paved the way to the development of thermally annealed Fe-ions implanted InGaAs(P) thin films [9,[11][12][13]. In previous work of our group, post-implantation rapid thermal annealing (RTA) was achieved to induce solid phase recrystallization in the film: this recrystallization was shown to improve the photocarriers mobility while preserving up to a certain extent the film resistivity and its ultrafast response [12,14].…”