Shift Of Photoluminescence Peak Energy Research Articles

Photoluminescence studies on Si-doped GaAs/Ge

Photoluminescence (PL) spectroscopy has been used to study the silicon incorporation in polar GaAs on nonpolar Ge substrates. Shifts of PL spectra towards higher energy with growth temperature, trimethylgallium (TMGa) and arsine (AsH3) mole fractions were observed. The full width at half maximum increases with increasing growth temperature, AsH3 and TMGa mole fractions. The peak at 1.49 eV has been attributed to band-to-acceptor transition involving residual carbon. The PL peak energy shifts towards higher energy with increasing growth temperature due to the increase in electron concentration. A vacancy control model may explain the PL shift towards higher energy with increasing AsH3 mole fraction. The PL peak shifts towards higher energy with increasing TMGa mole fraction. The experimental results about the growth temperature, trimethylgallium, and arsine mole fractions on silicon-doped GaAs on GaAs were presented for comparison. The outdiffusion of Ge into the GaAs epitaxial layer was hardly to be seen from the secondary ion mass spectroscopy result.

Band alignment in Si1−yCy/Si(001) heterostructures

Photoluminescence peak energy shifts under applied [110] and [100] uniaxial stress are interpreted within the framework of a multi-band Kohn–Luttinger model which takes into account the mixing of heavy, light, and spin-orbit split-off holes within the valence band. Experimental data are presented for 0.5%, 1%, and 1.7% Si1−yCy/Si samples which are best fitted with a conduction band offset of approximately 70%. At this value of the conduction band offset, we show that small amounts of space charge induced band bending are required to explain the experimentally observed results.

Dimensionality effects on strain for lattice-mismatched [formula omitted] quantum wires: The relationship between strain and 2D quantum confinement

Lateral size effects for optical response of lattice-mismatched InAsP InP quantum wires are investigated. We observed clear size-dependent blue shift in photoluminescence peak energy, which is markedly larger than lattice-matched quantum wires. High magnetic-field (28 T maximum) applied PL measurements clarified that the observed blue shift cannot be explained by the lateral quantum confinement effect. We calculated strain energy in lattice-mismatched quantum wires, and found that the sum of size-dependent strain energy and the lateral quantum confinement effects well explain the observed blue shift.

Photoluminescence Study on InGaAs/InP MQW Structure with F+, Ne+-Implant Induced Compositional Disordering

A photoluminescence (PL) study on InGaAs/InP multiple-quantum wells (MQW) structure with F+, Ne+ implant induced compositional disordering (IICD) is presented. The effects of energy shift of PL peak depend on ion dose, annealing conditions, target temperature and implanted ion species. The results indicate that the optimum annealing condition is approximately 750°C for 30 s, the ion dose which caused biggest blue shift is around 1 × 1014 cm-2 for room temperature implantation and 5 × 1014 cm-2 for elevated temperature of 200°C implantation. With the same condition of implantation and annealing, F+ and Ne+ implantation induced approximately the same blue shift of PL peak. This result suggests that the radiation enhanced diffusion by neutral ion implantation dominates the IICD processing. The secondary ion mass spectroscopy analysis indicates that the ion implantation caused slightly layer interdiffusion which makes the square potential well smear and results in the band gap blue shift.

Luminescence investigation on strained Si 1− xGe x/Si modulated quantum wells

Luminescence characterization is presented on potential-modulated strained Si 1− x Ge x /Si(100) quantum wells. Interwell coupling was studied in a series of coupled quantum wells (CQW) with an intervening Si barrier for symmetric and asymmetric configurations. Systematic red shift of photoluminescence peak energy was observed in symmetric CQWs with decreasing Si barrier width centered at CQW. Interwell coupling was further evidenced in asymmetric CQWs luminescence as spectral dominance switch between the narrower and the wider wells, reflecting the tunneling-controlled carrier transfer. Evolution of Kronig-Penney superlattice state was observed as consistent luminescence peak shift with change in the structural parameters. Diffusion induced blue-shift of luminescence peak amounting to 22 meV was observed.

Quantum Confinement in Coated Semiconductor Nano-Particles

ABSTRACTWe previously reported the synthesis and some properties of heterostructure nanoparticles, i.e. CdS coated with PbS (CdS/PbS). We report further characterization and investigation of the infrared photoluminescence (PL) of the CdS and coated CdS/PbS nanoparticles. This allows us to provide a more stringent test of the quantum confinement model. We consider the energy shift of the PL peak and the variation of the PL intensity correlated with the predictions of the quantum confinement model. The experimental results can be explained by this model of coated semiconductor nanoparticles.

Photoluminescence spectroscopy of near-surface quantum wells: Electronic coupling between quantized energy levels and the sample surface

Photoluminescence (PL) measurements have been used to examine the influence which the proximity of the sample surface bears on the radiative recombination occurring within a near-surface quantum well (QW). The InxGa1−xAs/GaAs system exhibits dramatic attenuation in PL intensity for surface barriers below 75 Å in thickness, without any significant shift in PL peak energy. However, as the GaAs surface barrier is reduced to zero, both In0.26Ga0.74As/GaAs and In0.1Ga0.9As/GaAs QWs reveal the development of an additional PL feature at an energy which coincides with that expected for direct band-to-band recombination within the strained InxGa1−xAs layer. PL measurements for chemically etched Al0.3Ga0.7As/GaAs near-surface QWs also show a lack of shift in PL peak energy, as the outer layer is thinned gradually.

Exciton Magnetoluminescence Studies in Ordered and Disordered In0.48Ga0.52P Semiconductor Alloys

ABSTRACTWe report the observation of magnetic-field dependent excitonic photoluminescence energies and linewidths in ordered and disordered In0.48Ga0.52P alloys (lattice matched to GaAs). The photoluminescence measurements were made at 1.4 K and the applied magnetic field ranged between 0 and 13.6 tesla. With increasing magnetic fields, we observe increasing photoluminescence linewidths for disordered alloys and decreasing photoluminescence linewidths for the ordered alloys. The magnetic field dependence of the photoluminescence peak-energy shifts for all samples (ordered and disordered) is in good agreement with theoretical considerations. The presence of CuPt-type ordering was confirmed by transmission electron microscopy.

Mass and dose dependence of ion-implantation-induced intermixing of GaAs/GaAlAs quantum-well structures

The influence of ion mass and dose on the intermixing of GaAs/GaAlAs quantum-well structures using photoluminescence (PL) and secondary-ion-mass spectroscopy (SIMS) techniques has been studied. Ga, Zn, Ar, Mg, Ne, and He ions are implanted in a single-quantum-well (SQW) structure at different doses. After annealing, the amount of intermixing between Al and Ga is extracted from the PL peak energy shift of the near-band-gap emission of the SQW. The measured Al diffusion length values ΔAl for different ion species agree with a simple model which assumes that the implantation damage in conjunction with low T (T<600 °C) defect diffusion is responsible for the mixing. We observe a similar dose dependence for ΔAl for all the above ions. For high implantation doses we have studied the mixing by Ar ions after implantation and annealing with SIMS. The SIMS data indicate that at high doses collisional mixing is the dominant mechanism for the disordering. Drastic mixing effects are obtained in the above quantum-well structures after high-temperature annealing of samples implanted with electrically active impurities (S,Si).

InGaAs/AWAsSb Heterostructures Lattice-Matched to InP GRown by Molecular Beam Epitaxy

ABSTRACTWe have successfully grown InGaAs/AIAsSb quantum-well (QW) structures lattice-matched to InP by molecular beam epitaxy for the first time. We studied the band-edge discontinuity and the interface abruptness of these heterostructures. A cross-sectional lattice image of InGaAs/AlAsSb QWs taken along the [100] axis showed atomically smooth heterointerfaces. The photoluminescence (PL) peak energy of the 20-nm-thick InGaAs well (0.758 eV) was lower than that of InGaAs bulk (0.799 eV), indicating that the InGaAs/AlAsSb system has a staggered lineup. The conduction band-edge discontinuity, ΔEc, was evaluated to be 1.74 ± 0.04 eV, which was derived from parameter fitting to the 4.2 K PL peak energy shifts of QWs as a function of InGaAs well width between 2.1 nm and 20 nm. The corresponding valence band-edge discontinuity, ΔEv, was 0.07 ± 0.02 eV. We also fabricated a resonant tunneling barrier structure of InGaAs (4.4 nm)/AlAsSb (2.9 nm), and obtained a very high peak-to-valley current ratio of 15 at 300 K.

Intermixing of InGaAs/InP multiple quantum well structures by Ga implantation

The effect of Ga implantation and thermal annealing on InGaAs/InP multiple quantum well structures is investigated by photoluminescence (PL) and sputtering Auger electron spectroscopy. It is found that the interdiffusion of both column III and column V atoms occurs at the interfaces between InP barrier and InGaAs well layers, but the degree of intermixing near the sample surface is small. The variations of PL peak energy shift with annealing and dose suggest that the PL peak shift is attributed to a combination of intermixing and stress.

Characterization of InP/GaAs epilayers grown on Si substrates by low-pressure organometallic vapor phase epitaxy

Heteroepitaxial growth of InP on Si with an intermediate GaAs buffer layer by low-pressure organometallic vapor phase epitaxy is reported. Excellent crystallinity of InP epilayers with specular surfaces can be reproducibly obtained. The carrier concentration profile shows that the carrier distribution in the InP layer is very uniform, while an apparent reduction in concentration occurs at the InP/GaAs interface. The 77 K photoluminescence (PL) of the InP layer exhibits a strong near-band-edge emission. No evident shift in PL peak energy for the InP/GaAs/Si sample compared with that for the InP homoepitaxial sample was first observed in this study. These results are superior to those reported previously for the InP/Si heteroepitaxy.

Growth and characterization of InP/GaAs epilayers on Si substrates by low-pressure metalorganic vapor phase epitaxy

Heteroepitaxial growth of InP on Si with an intermediate GaAs buffer layer by low-pressure metalorganic vapor phase epitaxy is reported. Single-crystal InP epilayers with specular surfaces can be reproducibly obtained. The uniform composition of this heterostructure was identified by the Auger depth profile. The best room-temperature electron mobility of the undoped InP epilayer can reach 3250 cm2/V·s with a carrier concentration of 1×1015 cm−3. It was found that the InP electron mobility is critically dependent on the growth temperature. The 77 K photoluminescence (PL) of the InP layer exhibits a strong near-band-edge emission. No evident shift in PL peak energy for the InP/GaAs/Si sample compared with that for the InP homoepitaxial sample was first observed in this study. An evident effect of the GaAs buffer-layer thickness on the InP optical quality is also demonstrated.