Photoreflectance characterisation of GaAs and GaAs/GaAIAs structures grown by MOCVD (original) (raw)
Related papers
Semiconductor heterostructures and device structures investigated by photoreflectance spectroscopy
In this review, we present the photoreflectance (PR) spectroscopy as a powerful tool for investigations of bulk semiconductors and semiconductor heterostructures. We discuss the application of PR technique to investigation of various properties of semiconductors, including the composition of multinary compounds, distribution of the built-in electric field and the influence of perturbations such as temperature, strain, pressure; low-dimensional structures such as quantum wells, multiple quantum wells and superlattices, quantum dots; and the structures of semiconductor devices like transistors and vertical/planar light emitting laser structures.
Photoreflectance study of GaAsSb∕InP heterostructures
Journal of Applied Physics, 2005
Photoreflectance (PR) spectroscopy experiments are reported on GaAsSb∕InP heterostructures. The GaAsSb PR spectrum is studied as a function of temperature and the transition nature is shown to change from Franz-Keldysh oscillations (FKO) at room temperature to a third derivative functional form (TDFF) line shape at low temperatures. Combining both analysis (FKO and TDFF) in the same sample, we derive internal electric field and phase values of the PR transition, together with accurate values for alloy band gap energy on the whole temperature range. Type II interface recombination is shown to reduce photovoltage effects as a function of temperature. FKO are found to appear for a very weak electric field (8kV∕cm) in the GaAsSb∕InP heterostructure, contrary to usual observations. This point is discussed in relation with the broadening parameter of the transition.
Photoreflectance characterization of OMVPE GaAs on Si
Journal of Crystal Growth, 1988
Photorefiectance, a contactless, non-destructive optical characterization tool, can be of great utility to the material scientist in identifying crystal growth problems and ascertaining material quality in a very short time. It provides a precise measurement of the spectral energy of the fundamental absorption edge and higher lying critical point transitions. Shifts in these energies are a measure of the built-in strain in strain-layered heterostructures. Moreover, the spectral energy of the so-called Franz-Keldysh oscillation extrema is directly related to the net carrier concentration of the semiconductor material under study. We have ased the Photoreflectance technique to determiae the crystal quality, the carrier concentration, and the built-in strain of epitaxial GaAs gro~,n by OMPVE on Si substrates. The study includes determination of these parameters as a function of various growth conditions, post-growth anneal cycle, and spot position on the wafer. Results are correlated with X-ray diffraction, and C-I/ measurements.
Photoreflectance and Raman Study of Surface Electric States on AlGaAs/GaAs Heterostructures
Journal of Spectroscopy, 2016
Photoreflectance (PR) and Raman are two very useful spectroscopy techniques that usually are used to know the surface electronic states in GaAs-based semiconductor devices. However, although they are exceptional tools there are few reports where both techniques were used in these kinds of devices. In this work, the surface electronic states on AlGaAs/GaAs heterostructures were studied in order to identify the effect of factors like laser penetration depth, cap layer thickness, and surface passivation over PR and Raman spectra. PR measurements were performed alternately with two lasers (532 nm and 375 nm wavelength) as the modulation sources in order to identify internal and surface features. The surface electric field calculated by PR analysis decreased whereas the GaAs cap layer thickness increased, in good agreement with a similar behavior observed in Raman measurements (IL-/ILOratio). When the heterostructures were treated by Si-flux, these techniques showed contrary behaviors. P...
Low-Temperature Photoluminescence of Mocvd GaAs Grown Directly on Si
MRS Proceedings, 1987
ABSTRACTWe present a systematic study of the low-temperature photoluminescence from undoped GaAs layers grown directly on Si substrates by MOCVD. GaAs layers from 100Å to 4 μm in thickness were deposited on Si substrates prepared with a variety of doping levels and orientations. The emission from thicker samples is dominated by pairs of lines in the band-edge region. Photoluminescence excitation measurements show that this multiplicity results from two regions in the material with different levels of strain. The stress-induced splitting of the valence band is also studied using excitation spectroscopy. In thinner samples we observe strong emission in the midgap range due to stoichiometric defects. The nature of the defects near the interface depends strongly on the character of the substrate.
physica status solidi (a), 2007
Pseudomorphic InGaAs/GaAs quantum wells (QWs) and self-assembled InAs quantum dots (QDs) were grown by molecular beam epitaxy (MBE) on GaAs(11n)A substrates. Photoreflectance spectroscopy was employed to investigate the transitions in the heterostructures. The transitions in QWs have two contributions, a blue shift due to the compressive strain, and a red shift due to the quantum confined Stark effect produced by the piezoelectric field. A traditional theoretical interpretation of the QWs transitions employing a simple well model with sharp interfaces shows discrepancies with the experimental results. In order to satisfactorily explain the transitions we proposed to include segregation effects of Indium at the wells interfaces. The matrix transfer method was implemented to numerically solve the Schrödinger equation taking into account In segregation effects by including an asymmetric potential well with a profile depending on the details of the In incorporation. With segregation effects included, the calculated transitions fit very well the PR spectra. On the other hand, the transitions in self-assembled QDs were obtained by fitting the PR spectra employing a first derivative line-shape function. For n = 2, 4, 5, two functions were required to fit the spectra. For n = 3 only one function was required, in agreement with the more uniform QDs size distribution observed by atomic force microscopy on GaAs(113)A.
Method for calculating photo- and electroreflectance spectra from semiconductor heterostructures
Physical Review B, 1995
A method for calculating photoand electrore8ectance spectra from weakly inhomogeneous layers of semiconductor heterostructures is developed. Transfer matrices are used in order to solve the propagation of light between di8'erent layers and perturbation theory in order to obtain the transfer matrix for a single layer. If applied to an infinite half space, the method reproduces the result by Aspnes and Frova [Solid State Commun. 7, 155 (1969)I. The electric field profiles of the heterostructures are calculated by means of an integral equation which holds under quite general conditions including incomplete dopant ionization and carrier degeneracy. The application of the general theory is demonstrated by calculating photore8ectance spectra of homogeneously n-doped semi-infinite GaAs samples with difFerent doping levels, and of a (Al, Ga)As heterostructure with an interface charge between bu8'er layer and substrate. Due to its speed and accuracy the method has the potential for an on-line simulation of photoand electrore8ectance spectra.