Evidence of phosphorus incorporation into InGaAs/InP epilayers after thermal annealing

Abstract

We report on Raman scattering measurements on annealed In 0.53 Ga 0.47 As/InP layers that reveal the outdiffusion of phosphorus from the substrate and its possible incorporation in substitutional positions in the In 0.53 Ga 0.47 As lattice. Raman signal associated with InP-like modes was detected in the annealed samples. The effect is also observed in samples where the substrate was protected by a SiN x :H capping and were annealed in arsenic atmosphere, thus ruling out the possibility of a surface contamination by atmospheric phosphorus evaporated from the InP substrate. Protruding regions of a few microns were observed on the surface, which were identified as misoriented In 1Ϫx Ga x P and InP crystals by means of micro-Raman measurements.

Atomic layer diffusion and electronic structure at In0.53Ga0.47As/InP interfaces

“…It is difficult to achieve abrupt interfaces in these structures because both group-III and group-V elements must be switched at the interface. 5 Others, citing Raman data, 6,7 have reported evidence of P incorporation into the InGaAs lattice at growth or anneal temperatures above 640°C. Along with minimizing chamber memory effects, this allows the new group-V element time to diffuse into the existing epilayer, possibly resulting in interfacial broadening.…”

Raman spectroscopy studies of dopant activation and free electron density of In0.53Ga0.47As via sulfur monolayer doping

“…10,11 This strong electron-phonon coupling makes Raman spectroscopy an excellent contact-less probe of carrier density, band bending, and crystallinity in binary and ternary III-V semiconductors. [10][11][12][13][14][15] In the ternary alloy In x Ga 1Àx As, which shows two distinct longitudinal optical modes, the phonon-plasmon coupling is complicated by the existence of a pronounced Landau damping regime corresponding to the decay of the plasmon into single particle excitations. 13,14 Cusco ´and co-workers have developed a wave-vector-dependent Lindhard-Mermin model for describing the lineshapes of the coupled modes in Si-doped In x Ga 1Àx As taking into account the nonparabolicity of the conduction band of In x Ga 1Àx As and the pronounced Landau damping in this system.…”

Determination of Free Electron Density in Sequentially Doped InxGa1-xAs by Raman Spectroscopy

“…In polar semiconductors characterized by an appreciable electronegativity difference between the cation and the anion, the longitudinal optic phonons establish a periodically varying macroscopic electric field that can strongly couple to the electron gas derived from free charge carriers subject to the plasmon frequency being comparable to the optical phonon frequencies. 9,10,14 For doped ternary semiconductors such as In x Ga 1Àx As, (Fig. 2), activated dopant concentrations deduced from the peak positions of the HFCM modes using the Lindhard-Mermin formalism (n RS ), additional charge carrier density introduced as a result of sulfur monolayer doping, sheet resistance values measured using the van der Pauw method, N eff values determined from Hall measurements, and estimated N eff values calculated by dividing the determined N eff values by the thickness of the In 0.53 Ga 0.47 As epilayer (200 Å ).…”

“…Raman measurements were performed at room temperature in backscattering geometry (selection rules permit the observation of only longitudinal optic modes for scattering from (100) In 0.53 Ga 0.47 As) using a Jobin Yvon Horiba LabRAM HR (Villeneuve d'Ascq, France) instrument coupled to an Olympus BX41 microscope with a 503 objective using 514.5 nm laser excitation from an Ar-ion laser, which provides a probe depth estimated to be $22.4 nm given the high optical absorption coefficient of In x Ga 1Àx As at 514.5 nm. 14 An 1800 lines/mm grating spectrometer equipped with a Peltier-cooled chargecoupled device (CCD) detector (Andor) was used to acquire spectra yielding a spectral resolution better than 2 cm À1 and spatial resolution of about 1 lm. The laser power was maintained below 10 mW to minimize local heating and photoexcitation of charge carriers in the highly doped samples.…”

“…Owing to its strongly plasmon-phonon coupled nature, the energy of the HFCM band is closely correlated to the free carrier density in In x Ga 1Àx As, thereby providing a sensitive contactless optical measure of the carrier concentration. 9,10,14 This allows Raman spectroscopy to serve as a direct measure of carrier concentration unlike techniques such as secondary ion mass spectrometry or glow discharge methods that provide an indication of the dopant concentration but do not discriminate between active (corresponding to dopants that have been incorporated in the desired lattice sites and have generated free carriers) and inactive dopants. Figure 2 shows the Raman spectra for Samples 1, 2, and 3 in the HFCM region with the corresponding spectra for their sequentially doped counterparts overlaid to illustrate the pronounced modification of these spectral features upon sulfur monolayer doping.…”