Showing papers on "Quantum well published in 1987"
TL;DR: The fundamental relationship between radiative lifetime and spectral linewidth of freeexcitons is demonstrated theoretically and experimentally for quasi 2D excitons in GaAs/AlGaAs quantum wells.
Abstract: The fundamental relationship between radiative lifetime and spectral linewidth of free excitons is demonstrated theoretically and experimentally for quasi 2D excitons in GaAs/AlGaAs quantum wells.
820 citations
TL;DR: In this article, the authors present an overview of topics related to one of the fundamental parameters for semiconductor lasers-the linewidth broadening factor α that describes the coupling between carrier-concentration-induced variations of real and imaginary parts of susceptibility.
Abstract: The objective of this paper is to present an overview of topics related to one of the fundamental parameters for semiconductor lasers-the linewidth broadening factor α that describes the coupling between carrier-concentration-induced variations of real and imaginary parts of susceptibility. After introducing the definition of α and discussing its dependence on carrier concentration, photon energy, and temperature, we give a short historical summary on how the concept of α evolved over the past two decades. This is followed by a discussion of α dependence on device structure in gain-guided and subdimensional lasers (quantum wells and quantum wires). The bulk of the paper is devoted to a detailed review of laser properties influenced by α and of associated methods of estimating the value of α. Results of measurements reported to date are collected and the most reliable methods are indicated.
646 citations
TL;DR: In this paper, the influence of interface roughness on the mobility of two-dimensional electrons in modulation-doped AlAs/GaAs quantum wells was studied experimentally and theoretically.
Abstract: We study experimentally and theoretically the influence of interface roughness on the mobility of two‐dimensional electrons in modulation‐doped AlAs/GaAs quantum wells. It is shown that interface roughness scattering is the dominant scattering mechanism in thin quantum wells with a well thickness Lw<60 A, where electron mobilities are proportional to L6w, reaching 2×103 cm2/V s at Lw∼55 A. From detailed comparison between theory and experiment, it is determined that the ‘‘GaAs‐on‐AlAs’’ interface grown by molecular beam epitaxy has a roughness with the height of 3–5 A and a lateral size of 50–70 A.
600 citations
TL;DR: In this article, a 10.8 μm superlattice infrared detector based on doped quantum wells of GaAs/AlGaAs was proposed, which achieved a narrow bandwidth (10%) photosensitivity with a responsivity of 0.52 A/W and an estimated speed of 30 ps.
Abstract: We demonstrate a novel 10.8 μm superlattice infrared detector based on doped quantum wells of GaAs/AlGaAs. Intersubband resonance radiation excites an electron from the ground state into the first excited state, where it rapidly tunnels out producing a photocurrent. We achieve a narrow bandwidth (10%) photosensitivity with a responsivity of 0.52 A/W and an estimated speed of 30 ps.
533 citations
TL;DR: Observation experimentale de la bistabilite intrinseque dans une structure Al 0-4 Ga 0,6 As/GaAs/Al 0,4 Ga0,4 As; interpretation en termes de variations de l'energie des etats electroniques dans le puits en fonction de the densite du courant-tunnel.
Abstract: A simple quantum system, the semiconductor-based double-barrier resonant-tunneling structure, exhibits intrinsic bistability which we attribute to the feedback dependence of the energy of the electronic states in the well on the tunneling current density.
387 citations
TL;DR: In this article, the authors calculate the electric field dependence of the linear and the third-order nonlinear intersubband optical absorption coefficients of a semiconductor quantum well in the infrared regime.
Abstract: Analytic forms of the linear and the third-order nonlinear optical intersubband absorption coefficients are obtained for general asymmetric quantum well systems using the density matrix formalism, taking into account the intrasubband relaxation. Based on this model, we calculate the electric field dependence of the linear and the third-order nonlinear intersubband optical absorption coefficients of a semiconductor quantum well. The energy of the peak optical intersubband absorption is around 100 meV (wavelength is 12.4 μm). Thus, electrooptical modulators and photodetectors in the infrared regime can be built based on the physical mechanisms discussed here. The contributors to the nonlinear absorption coefficient due to the electric field include 1) the matrix element variation and 2) the energy shifts. Numerical results are illustrated.
384 citations
TL;DR: In this article, the infrared intersubband absorption at 8.2 μm in doped GaAs/AlAs quantum well superlattices was measured, with 95% of the incident infrared energy being absorbed.
Abstract: We have measured the infrared intersubband absorption at 8.2 μm in doped GaAs/AlAs quantum well superlattices. Waveguide geometry experiments demonstrate strong absorption with 95% of the incident infrared energy being absorbed.
291 citations
TL;DR: InGaAs/InP quantum well layers grown by gas source molecular beam epitaxy have been used to fabricate quantum wires and boxes with transverse dimensions as small as ∼300 A.
Abstract: InGaAs/InP quantum well layers grown by gas source molecular beam epitaxy have been used to fabricate quantum wires and boxes with transverse dimensions as small as ∼300 A. These artificial structures exhibit intense low‐temperature photoluminescence and show exciton shifts of 8–14 meV expected of low dimensional confinement. Low surface recombination velocity characteristic of InP and its alloys should allow luminescence studies of features as small as ∼30 A under moderate excitation intensities.
280 citations
TL;DR: In this article, the authors observed Stark shifts of quantum well intersubband transitions in a perpendicular electric field and applied these tunable transitions to high-speed infrared light modulators.
Abstract: We have observed Stark shifts of quantum well intersubband transitions in a perpendicular electric field. Two samples consisting of 100 and 120 A GaAs quantum wells separated by 350 A AlGaAs barriers showed optical absorption peaks at 11.1 and 13.9 μm, respectively. In an electric field of 36 kV/cm, the 13.9 μm peak shifted to 13.7 μm and the 11.1 μm shifted to 11.0 μm, in good agreement with theoretical calculations. These tunable transitions can be applied to high‐speed infrared light modulators.
270 citations
TL;DR: In this paper, the critical width for misfit dislocation generation was determined for molecular beam epitaxy grown strained InxGa1−xAs (0.1
Abstract: The critical width Lc for misfit dislocation generation has been determined for molecular beam epitaxy grown strained InxGa1−xAs (0.1
226 citations
TL;DR: In this article, an analytic expression for the nonlinear gain in multimode semiconductor lasers using the density-matrix formalism was obtained, and the agreement between the theoretical and experimental values supported the hypothesis that spectral hole burning is the dominant mechanism for the gain nonlinearities in semiconductor laser.
Abstract: The gain spectrum in semiconductor lasers is affected by the intensity-dependent nonlinear effects taking place due to a finite intraband relaxation time of charge carriers. We obtain an analytic expression for the nonlinear gain in multimode semiconductor lasers using the density-matrix formalism. In general, the nonlinear gain is found to consist of the symmetric and asymmetric components. The asymmetry does not have its origin in the carrier-induced index change, but is related to details of the gain spectrum. The general expression for the nonlinear gain is used to discuss the range of single-longitudinal-mode operation of distributed feedback lasers. It is also used to obtain an analytic expression for the self-saturation coefficient and to compare the predicted value to the experimental value for both GaAs and InGaAsP lasers. The agreement between the theoretical and the experimental values supports the hypothesis that spectral hole burning is the dominant mechanism for the gain nonlinearities in semiconductor lasers.
TL;DR: A tunneling escape rate 1/${T} of electrons from a single quantum well through thin barriers was successfully determined by measurement and analysis of the lifetime of electrons generated in 6.2-nm GaAs single quantum wells by a picosecond laser pulse.
Abstract: A tunneling escape rate 1/${\mathrm{\ensuremath{\tau}}}_{\mathrm{T}}$ of electrons from a single quantum well through thin barriers was successfully determined by measurement and analysis of the lifetime ${\mathrm{\ensuremath{\tau}}}_{\mathrm{e}}$ of electrons generated in 6.2-nm GaAs single quantum wells by a picosecond laser pulse. The measured ${\mathrm{\ensuremath{\tau}}}_{\mathrm{e}}$ was found to decrease systematically as the AlAs barrier thickness ${\mathrm{L}}_{\mathrm{B}}$ was reduced. The ${\mathrm{\ensuremath{\tau}}}_{\mathrm{e}}$ for ${\mathrm{L}}_{\mathrm{B}}$4 nm was found to agree very well with the lifetime ${\mathrm{\ensuremath{\tau}}}_{\mathrm{T}}$ predicted from the energy width of the resonance transmission. Irrelevance of coherence versus incoherence in the tunneling escape process is also pointed out.
TL;DR: In this paper, a low-temperature optical transmission spectra of several In(x)Ga(1-x)/GaAs strained MQWs with x = 0.13-0.19 and well widths of 85-213 A have been measured.
Abstract: Low-temperature optical transmission spectra of several In(x)Ga(1-x)/GaAs strained MQWs with x = 0.13-0.19 and well widths of 85-213 A have been measured. The excitonic transitions up to 3C-3H were observed along with steplike structures corresponding to band-to-band transitions, identified as 1C-1L transitions. By fitting experimental results to the calculations, it is concluded that the light holes are in the GaAs barrier region (type II MQW), and the valence-band offset is determined to be 0.30. Attention is given to a possible system in which the transition from type I to type II for light holes might be observed.
01 Jan 1987
TL;DR: The first € price and the £ and $ price are net prices, subject to local VAT as discussed by the authors, and the first £ and £ price is net price subject to £ and US VAT.
Abstract: The first € price and the £ and $ price are net prices, subject to local VAT. Prices indicated with * include VAT for books; the €(D) includes 7% for Germany, the €(A) includes 10% for Austria. Prices indicated with ** include VAT for electronic products; 19% for Germany, 20% for Austria. All prices exclusive of carriage charges. Prices and other details are subject to change without notice. All errors and omissions excepted. E.E. Mendez, K. von Klitzing Physics and Applications of Quantum Wells and Superlattices
TL;DR: In this article, the photoluminescence of nominally undoped quantum wells is studied as a function of temperature and excitation power, and the role of an excitonic process in 4K radiative recombinations is pointed out.
Abstract: The properties of InGaAs‐InP single quantum wells have been studied by using the photoluminescence technique. Samples were grown by atmospheric pressure metalorganic vapor phase epitaxy. The photoluminescence of nominally undoped quantum wells is studied as a function of temperature and excitation power. The role of an excitonic process in 4‐K radiative recombinations is pointed out. The best linewidth obtained for a 140‐A well is 4.5 meV, fairly close to the limit imposed by alloy fluctuations in the InGaAs thick layers. Radiative recombination is more and more efficient with decreasing well thickness and higher than in InGaAs bulk material.
TL;DR: In this paper, a GaAs/AlGaAs superlattice heterostructures with layer thickness ≲100 A were grown by molecular beam epitaxy on nonplanar GaAs substrates.
Abstract: GaAs/AlGaAs superlattice heterostructures with layer thicknesses ≲100 A were grown by molecular beam epitaxy on nonplanar GaAs substrates. The resulting superlattices exhibit different periods, depending on the crystal plane on which they grow. Period variation of more than 50%, from 180 to 80 A, was obtained for adjacent superlattice sections. The transition between regions of different periodicity was mostly smooth and occurred within lateral dimensions ≲100 A. Our results suggest that molecular beam epitaxy of superlattice heterostructures on patterned substrates provides a method for obtaining controllable lateral variations in physical properties which depend on the superlattice period. In particular, by growing quantum well heterostructures on nonplanar substrates, it might be possible to utilize the strong dependence of the carrier confinement energy on the well thickness in order to achieve lateral carrier confinement.
TL;DR: In this paper, a semi-empirical calculation of the refractive index changes induced by a perpendicular electric field in quantum wells is presented. But this calculation is based on experimental electroabsorption data, together with absorption sum rules that have recently been developed.
Abstract: We have performed a semi‐empirical calculation of the refractive index changes induced by a perpendicular electric field in quantum wells. This calculation is based on experimental electroabsorption data, together with absorption sum rules that have recently been developed. We find good agreement with published experimental results. Our results are important to the development of electro‐optic and high‐speed electroabsorption quantum well devices.
TL;DR: In this article, the authors achieved a high responsivity, R=1.9 A/W, 10 μm infrared detector using intersubband absorption in GaAs/AlxGa1−xAs quantum well superlattices.
Abstract: We have achieved a high responsivity, R=1.9 A/W, 10 μm infrared detector using intersubband absorption in GaAs/AlxGa1−xAs quantum well superlattices. The photocurrent is produced by intersubband absorption followed by efficient photoexcited tunneling. This responsivity is nearly four times higher than our previous results and has been obtained by using thicker and higher AlxGa1−xAs superlattice barriers thereby reducing the dark current and allowing the detector to be operated at higher biases.
TL;DR: In this paper, a monocrystalline indium phosphide substrate of a predetermined conductivity type is used for a semiconductor laser, where a wide range of laser emission wavelengths can be obtained by varying the composition of monocrystaline alloys employed as semiconductor material.
Abstract: A semiconductor laser wherein a wide range of laser emission wavelengths can be obtained by varying the composition of monocrystalline alloys employed as semiconductor material. The semiconductor structure comprises on a monocrystalline indium phosphide substrate of a predetermined conductivity type successive epitaxial layers consisting of a first confinement layer of the same conductivity type, an active layer having the formula (Gax Al1-x)0.47 In0.53 As where x is within the range of 0 to 0.27, and a second confinement layer of opposite conductivity type. The confinement layers are composed of either InP or a ternary alloy Al0.47 In0.53 As or a quaternary alloy Gax' Al1-x' Asy' Sb1-y' where x' and y' are chosen so that the material should have a predetermined crystal lattice and an energy gap of greater width than the substrate material.
TL;DR: In this article, the implementation of °-function-like doping profiles during molecular beam epitaxy (MBE) of GaAs by using Si donors and Be acceptors is employed to generate V-shaped potential wells with a quasi-two-dimensional electron (hole) gas and to create a new GaAs sawtooth doping superlattice with strongly reduced energy gap.
TL;DR: For increasing electric field the absorption peak corresponding to the transition of states 1\ensuremath{\rightarrow}2 is shifted higher in energy and the peak amplitude is increased and these features are different from those of the exciton absorption.
Abstract: We present new results for the electric field dependence of the intersubband optical absorption within the conduction band of a quantum well. We show that for increasing electric field the absorption peak corresponding to the transition of states 1\ensuremath{\rightarrow}2 is shifted higher in energy and the peak amplitude is increased. These features are different from those of the exciton absorption. It is also found that the transition 1\ensuremath{\rightarrow}3, forbidden when F=0, is possible when F is nonzero.
TL;DR: In this article, a novel GaAs/AlGaAs coupled quantum well structure, consisting of two 46 A wells separated by a 11.5 A barrier, was embedded in a leaky waveguide.
Abstract: A novel GaAs/AlGaAs coupled quantum well structure, consisting of two 46 A wells separated by a 11.5 A barrier, was embedded in a leaky waveguide. Polarization anisotropy and quantum‐confined Stark effect absorption changes are observed, and a 14:1 modulator is demonstrated operating at the peak of the first light‐hole transition. Although the lowest energy transitions behave as predicted by tunneling resonance calculations, higher energy states exhibit unusual behavior due to valence‐band mixing.
TL;DR: In this article, the first observation of the quantum constrained Stark effect in InGaAs/InP multiple quantum wells grown by organometallic vapor phase epitaxy was reported, both in transmission and photoconductivity measurements.
Abstract: We report the first observation of the quantum‐confined Stark effect in InGaAs/InP multiple quantum wells grown by organometallic vapor phase epitaxy. The effect is observed both in transmission and photoconductivity measurements. The observed spectral shift agrees with the theory.
TL;DR: In this article, the interband optical absorption of a nonuniform semiconductor quantum dot system is calculated and the effect of dot size variation on the resolvability of the absorption peaks is estimated.
Abstract: The interband optical absorption of a nonuniform semiconductor quantum dot system is calculated. The effect of dot size variation on the resolvability of the absorption peaks is estimated. The dots are assumed to be cubic, with a size distribution described by a Gaussian function. It is shown that the total absorption spectrum of such a dot system depends strongly on the dot size distribution described by the parameter ξ, the ratio of the standard deviation of the dot size to the average dot size of the system. The range of ξ values for which the absorption peaks are resolvable is given.
TL;DR: In this article, a quantum constrained Stark effect electroabsorption modulator consisting of quantum wells of AlGaAs and GaAs on an epitaxial multilayer dielectric mirror, all grown by molecular beam epitaxy, was demonstrated.
Abstract: We demonstrated a quantum‐confined Stark effect electroabsorption modulator consisting of quantum wells of AlGaAs and GaAs on an epitaxial multilayer dielectric mirror, all grown by molecular beam epitaxy. The resulting reflection modulator avoids problems of substrate absorption, and has relatively high contrast ratio (up to ∼8:1 with peak reflectivity of 25% at 853 nm) because the light passes twice through the quantum wells. Reflection modulators are of interest for bidirectional communication systems, in parallel arrays of optical switching and processing devices and for optical interconnects. For the latter there exists the possibility of this device grown on the same substrate alongside a GaAs integrated circuit or even on Si substrates.
TL;DR: In this article, the columnar structure of quantum well structures are reported for the first time, and the dependence of the lateral extension of these islands on growth conditions is investigated, for fixed growth rate rs≊0.5 ML/s the mean island size decreases from 6 −7 μm to 2 μm upon an increase of growth temperature from Tg=600 to 660 ǫ°C.
Abstract: Direct images of growth islands differing by 2.8 A [1 monolayer (ML)] height at GaAs/AlGaAs heterointerfaces and of the columnar structure of quantum wells are reported for the first time. The structures are grown by molecular‐beam epitaxy (MBE) with interruptions of the growth of ≊2 min at the interfaces. The method used to obtain these images is scanning cathodoluminescence. The dependence of the lateral extension of these islands on growth conditions is investigated. For fixed growth rate rs≊0.5 ML/s the mean island size decreases from 6–7 μm to 2 μm upon an increase of growth temperature from Tg=600 to 660 °C. Apparently the growth process changes from a planar to a three‐dimensional one. For low‐growth temperature and rate the lateral extension of such islands can be larger than the carrier diffusion length. Under these conditions interisland thermalization of carriers is largely suppressed. Quantitative information on the reduction of roughness of the quantum well interfaces with increasing growth i...
TL;DR: In this paper, the critical layer thickness (CLT) for single strained-layer epitaxy in the InGaAs/GaAs system was determined by two sensitive techniques: Hall-effect measurements at 77 K and photoluminescence microscopy.
Abstract: We report accurate determination of the critical layer thickness (CLT) for single strained‐layer epitaxy in the InGaAs/GaAs system. Our samples were molecular beam epitaxially grown, selectively doped, single quantum well structures comprising a strained In0.2Ga0.8As layer imbedded in GaAs. We determined the CLT by two sensitive techniques: Hall‐effect measurements at 77 K and photoluminescence microscopy. Both techniques indicate a CLT of about 20 nm. This value is close to that determined previously (∼15 nm) for comparable strained‐layer superlattices, but considerably less than the value of ∼45 nm suggested by recent x‐ray rocking‐curve measurements. We show by a simple calculation that photoluminescence microscopy is more than two orders of magnitude more sensitive to dislocations than x‐ray diffraction. Our results re‐emphasize the necessity of using high‐sensitivity techniques for accurate determination of critical layer thicknesses.
TL;DR: In this article, a modification-doped GaAs heterostructures with low-temperature electron mobilities of 5.0×106 cm2/V at a two-dimensional electron areal density of 1.6×1011 cm−2 were made.
Abstract: Modulation‐doped GaAs heterostructures with low‐temperature electron mobilities of 5.0×106 cm2/V s at a two‐dimensional electron areal density of 1.6×1011 cm−2 have been made. The mobilities are the highest ever observed in a semiconductor. Multiple quantum wells of GaAs prepared by similar methods showed electron mobilities up to 0.54×106 cm2/V s at an areal density of 5.3×1011 cm−2 per layer, which also exceeds any mobility value previously reported for multiple well structures. The structures were grown by molecular beam epitaxy with an atomic‐plane sheet‐doping technique.