Abstract
The authors have studied the impact of epilayer strain on the deposition of InAs/GaAs on (100) and (111)B with 2° offset toward⟨2-1-1⟩ surfaces. Consequences of a 7% lattice mismatch between these orientations in the form of three-dimensional growth are less apparent for (111)B with 2° offset toward⟨2-1-1⟩ surfaces compared to (100). By exploring a range of molecular beam epitaxy process parameters for InAs/GaAs growth and utilizing scanning electron microscopy, atomic force microscopy, and Raman spectroscopy to evaluate the quality of these strained layers, the authors develop empirical models that describe the influence of the process conditions in regards to surface roughness with >92% accuracy. The smoothest InAs/GaAs samples demonstrated average surface roughness of 0.08 nm for 10 μm2 areas, albeit at very low deposition rates. The authors have found the most important process conditions to be substrate temperature and deposition rate, leading us to believe that controlling diffusion length may be the key to reducing defects in severely strained structures. InGaAs/AlGaAs quantum cascade laser structures were also produced on (111)B with 2° offset toward⟨2-1-1⟩ to take advantage of the piezoelectric effect, and the modified laser transitions due to these effects were observed.
Highlights
Indium arsenide (InAs) semiconductor devices that operate in the mid-infrared region are of interest, for applications that include environmental monitoring, infrared countermeasures, and thermal imaging, as well as free space optics.1 These technologies are naturally leading the way toward highly integrated systems that include spectral sensitivity, temporal control, and spatial resolution
By exploring a range of molecular beam epitaxy process parameters for InAs/GaAs growth and utilizing scanning electron microscopy, atomic force microscopy, and Raman spectroscopy to evaluate the quality of these strained layers, the authors develop empirical models that describe the influence of the process conditions in regards to surface roughness with >92% accuracy
Utilization of the piezoelectric effect in multiquantum well structures introduces a new dimension in photonic device design
Summary
Indium arsenide (InAs) semiconductor devices that operate in the mid-infrared region are of interest, for applications that include environmental monitoring, infrared countermeasures, and thermal imaging, as well as free space optics. These technologies are naturally leading the way toward highly integrated systems that include spectral sensitivity, temporal control, and spatial resolution. Several groups have explored the various process ranges for arsenic-based material and found that good structural and electrical characteristics require lower arsenic overpressure along with higher growth temperature, which depends on the orientation angle of the (111) substrate.24,25 These conditions are contrary to the conditions necessary for growth on (100) surfaces. With stringent control of molecular beam epitaxy process parameters and understanding of the growth kinetics, excellent material quality for strained quantum cascade laser structures can be obtained.. Molecular beam epitaxy conditions are explored for strained InAs deposition on GaAs (111)B with 2 offset towardh2-1-1i surfaces that introduce a promising piezoelectric feature. The key to extending device performance in these photonic structures is to address the limitations in the conduction band offset of AlGaAs/GaAs, while including resonant subbands in the active region. The (E4-E2) optical transition becomes likely for photon generation (laser output)
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