MeV oxygen ion implantation induced compositional intermixing in AlAs/GaAs superlattices

We present in this letter an investigation of compositional intermixing in AlAs/GaAs superlattices induced by 2 MeV oxygen ion implantation. The results are compared with implantation at 500 keV. In addition to Al intermixing in the direct lattice damage region by nuclear collision spikes, as is normally present in low-energy ion implantation, Al interdiffusion has also been found to take place in the subsurface region where MeV ion induced electronic spike damage dominates and a uniform strain field builds up due to defect generation and diffusion. Uniform compositional intermixing of the superlattices results after subsequent thermal annealing when Al interdiffusion is stimulated through recovery of the implantation-induced lattice strain field, the reconstruction and the redistribution of lattice defects, and annealing of lattice damage

Influence of substrate temperature on lattice strain field and phase transition in MeV oxygen ion implanted GaAs crystals

A detailed study of the influence of substrate temperature on the radiation-induced lattice strain field and crystalline-to-amorphous (c-a) phase transition in MeV oxygen ion implanted GaAs crystals has been made using channeling Rutherford backscattering spectroscopy, secondary ion mass spectrometry, and the x-ray rocking curve technique. A comparison has been made between the cases of room temperature (RT) and low temperature (LT) (about 100 K) implantation. A strong in situ dynamic annealing process is found in RT implantation at a moderate beam current, resulting in a uniform positive strain field in the implanted layer. LT implantation introduces a freeze-in effect which impedes the recombination and diffusion of initial radiation-created lattice damage and defects, and in turn drives more efficiently the c-a transition as well as strain saturation and relaxation. The results are interpreted with a spike damage model in which the defect production process is described in terms of the competition between defect generation by nuclear spikes and defects diffusion and recombination stimulated by electronic spikes. It is also suggested that the excess population of vacancies and their complexes is responsible for lattice spacing expansion in ion-implanted GaAs crystals

High efficiency single quantum well graded-index separate-confinement heterostructure lasers fabricated with MeV oxygen ion implantation

Single quantum well AlGaAs/GaAs graded-index separate-confinement heterostructure lasers have been fabricated using MeV oxygen ion implantation plus optimized subsequent thermal annealing. A high differential quantum efficiency of 85% has been obtained in a 360-µm-long and 10-µm-wide stripe geometry device. The results have also demonstrated that excellent electrical isolation (breakdown voltage of over 30 V) and low threshold currents (22 mA) can be obtained with MeV oxygen ion isolation. It is suggested that oxygen ion implantation induced selective carrier compensation and compositional disordering in the quantum well region as well as radiation-induced lattice disordering in AlxGa1–xAs/GaAs may be mostly responsible for the buried layer modification in this fabrication process

Amorphization and recrystallization in MeV ion implanted InP crystals

A comprehensive study of MeV-^(15)N-ion-implanted InP by a variety of analytical techniques has revealed the physical processes involved in MeV ion implantation into III-V compound semiconductors as well as the influence of post-implantation annealing. It provides a coherent picture of implant distribution, structural transition, crystalline damage, and lattice strain in InP crystals induced by ion implantation and thermal annealing. The experimental results from the different measurements are summarized in this report. Mechanisms of amorphization by implantation and recrystallization through annealing in MeV-ion-implanted InP are proposed and discussed in light of the results obtained

Characterization of high-energy heavy-ion implanted InP crystals by a variety of techniques

MeV ion implantation into InP compound semiconductor crystals with 5 MeV nitrogen ions has been investigated. The subsequent characterization was undertaken by a variety of techniques such as nuclear resonant reaction analysis, channeling Rutherford backscattering spectrometry, X-ray rocking curve measurement and cross-sectional transmission electron microscopy. These techniques have clearly revealed substantial changes in structural properties and radiation-induced damage distribution as well as the influence of post-implantation annealing in ^(15)N ion-implanted InP samples. The results from these measurements, which are presented in this paper, are shown to be consistent with each other, and have led to a coherent description of the effects of the implantation and subsequent annealing. In a practical sense this has demonstrated the complementary nature of the analytical capabilities of all of these techniques used for the investigation of the processes involved in high-energy heavy-ion implantation

Direct determination of Al content in molecular-beam epitaxially grown AlxGa1–xAs (0<=x<=1) by nuclear resonant reaction analysis and x-ray rocking curve techniques

The techniques of nuclear resonant reaction analysis (NRRA) using 27Al(p,gamma)28Si and x-ray rocking curve (XRC) based on double-crystal diffractometry have been utilized to determine directly the Al concentration and its depth distribution in molecular-beam epitaxially (MBE) grown AlxGa1–xAs/GaAs heterojunctions. Combination of these two methods has revealed a linear relationship between the Al mole fraction and the lattice strain. This can eliminate the need for assuming that Vegard's law holds and that extrapolated elastic coefficients are accurate. The result supports that both of these two techniques provide an accurate determination of the absolute Al content and crystalline quality in AlxGa1–xAs/GaAs throughout the entire composition range (0<=x<=1) as well as profiling the Al distribution. In addition, significant depth fluctuations in the Al mole fraction in some samples have been probed by the NRRA technique as well as by the XRC. The result suggests that a reliable and accurate measurement must be undertaken to ensure the control of the required Al distribution, which is necessary for the high performance of many devices

Fabrication of GaAs/AlGaAs Quantum Well Lasers with MeV Oxygen Ion Implantation

MeV oxygen ion implantation in GaAs/ AlGaAs has been shown to provide a simple and very promising technique for quantum well laser fabrication. A 10μm stripe single quantum well (SQW) graded-index separation confinement heterostructure (GRINSCH) laser made in this way has achieved high performance with high quantum differential efficiency, low threshold current and good electrical isolation characteristics. MeV oxygen ion implantation with optimum thermal annealing produces a deep buried electrical isolation layer in n-type GaAs and reduces optical absorption in GaAs/AlGaAs quantum well structures. Ion implantation stimulated compositional disordering as well as implanted oxygen-related deep level traps may be considered as important effects for electrical and optical modification of interfaces in GaAs and AlGaAs