Soohaeng Cho

Determination of the pyroelectric coefficient in strained InGaAs/GaAs quantum wells grown on (111)B GaAs substrates

We report an experimental determination of the pyroelectric coefficient for strained InGaAs layers in a pseudomorphic piezoelectric In0.17Ga0.83As/GaAs multiquantum well in a p-i-n diode configuration which was grown on a (111)B GaAs substrate by molecular-beam epitaxy. By analyzing the Franz–Keldysh oscillations in the photoreflectance spectra over the temperature range 11–300 K, we obtained the temperature dependence of the piezoelectric field, from which the temperature variation of the piezoelectric constant e14 was deduced. A linear dependence of e14 with temperature was observed. Therefore, the strain-induced component of the pyroelectric coefficient of (9.3±0.3)×10−7 C/m2 K was determined for this material system.

Interfacial properties of strained piezoelectric InGaAs∕GaAs quantum wells grown by metalorganic vapor phase epitaxy on (111)AGaAs

In this work we employed photoreflectance spectroscopy over the temperature range 11-300K to investigate the heterointerfaces of a strained piezoelectric InGaAs∕GaAs single quantum well structure grown on a (111)AGaAs substrate by metalorganic vapor phase epitaxy. Photoreflectance spectroscopy measurements in combination with a theoretical analysis using the quantum well structural parameters obtained by high-resolution x-ray diffractometry enabled us to evaluate separately the abruptness and roughness of the quantum well interfaces. The excellent agreement between the experimental and calculated transition energies for a quantum well structure with a well width of 41A and 13% In demonstrates that the heterointerfaces are abrupt. From a theoretical analysis of the temperature dependence of the photoreflectance broadening parameters, based on the Bose-Einstein phonon-coupling model, we determined the longitudinal optical phonon energy and the electron-phonon coupling strength. This analysis shows an interf...

Metalorganic vapor phase epitaxy growth and properties of GaAs/AlGaAs and InGaAs/GaAs quantum well structures on (111)A GaAs substrates

We review the recent advances in the fabrication and properties of GaAs/AlGaAs and InGaAs/GaAs quantum well (QW) structures grown on (111)A GaAs substrates by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE). We show that a 25-period GaAs/AlGaAs multi-QW (MQW) structure was fabricated with good crystal quality, high photoluminescence (PL) emission intensity and monolayer (ML) interfacial roughness. A PL full width at half maximum (FWHM) of 10.5 meV was achieved for a 25-period MQW with a well width of 44 A. This is the narrowest linewidth reported to date for any similar structures grown on (111)A or B substrates by any growth technique. We also report the properties of an InGaAs/GaAs single quantum well structure grown on (111)A GaAs. For this structure, the PL FWHM value was 9.1 meV, corresponding to a 1 ML interfacial roughness for a well width of 41 A. This is the first demonstration of an InGaAs/GaAs quantum well structure grown on (111)A or (111)B GaAs by MOVPE.

Interfacial properties of (111)A GaAs/AlGaAs multiquantum-well structures grown by metalorganic vapor phase epitaxy

We present the heterointerfacial properties of GaAs/AlGaAs multiquantum-well structures grown by atmospheric-pressure metalorganic vapor phase epitaxy on (111)A GaAs substrates at a relatively low growth temperature of 600 °C. For a 25-period GaAs/Al0.27Ga0.73As multiquantum-well structure with a well width of 44 A, a photoluminescence linewidth of 10.5 meV was observed, which is smaller than previously reported for a similar GaAs/AlGaAs multiquantum-well structure grown by molecular beam epitaxy on (111)A GaAs. As this linewidth corresponds to a combined well-width fluctuation and interfacial roughness throughout the 25 periods of at most ±1 monolayer, it is concluded that epitaxial growth on the (111)A surface can result in high-quality heterointerfaces, particularly at low growth temperatures.

Confirmation of the pyroelectric coefficient of strained InxGa1−xAs/GaAs quantum well structures grown on (111)B GaAs by differential photocurrent spectroscopy

In this work we used the differential photocurrent technique to measure the strain-induced piezoelectric field in pseudomorphic InxGa1−xAs/GaAs heterostructures grown by molecular beam epitaxy on (111)B GaAs substrates. Single and multiple quantum well p–i–n diodes with two different In fractions in the well were analyzed in the temperature range of 25–300 K. Our results for a sample with a 17% In fraction confirm the previously reported value of the pyroelectric coefficient for a similar sample obtained by photoreflectance spectroscopy, hence, the equivalence of the differential photocurrent and photoreflectance techniques is also demonstrated. For a sample with 21% In, we report experimental determination of the temperature dependence of the piezoelectric constant and, therefore, of the strain-induced component of the pyroelectric coefficient.

Piezoelectric InGaAs/GaAs/AlGaAs quantum well lasers grown on (111)A GaAs by metalorganic vapor phase epitaxy

This presents the properties of semiconductor double confinement strained PE InGaAs/GaAs/AlGaAs QW laser diodes grown on (111)A GaAs by MOVPE. The QW laser were grown on [111]A-oriented GaAs substrates and were extensively analyzed before laser fabrication by photoluminescence, high-resolution X-ray diffractometry, and transmission electron microscopy and was shown that these strained QWs have excellent interfacial properties and are fully strained without any evidence of strain relaxation. The optical and electrical characteristics of these lasers at low temperature and room temperature lasing in the 1.0-1.1/spl mu/m wavelength region were also presented.

Photoreflectance evaluation of MOVPE AlGaAs/GaAs multiple quantum wells on (111)A GaAs

Abstract The Photoreflectance (PR) technique was applied to evaluate a 25-period Al 0.27 Ga 0.73 As/GaAs multiquantum-well (MQW) structure with a well length of 55 A grown by atmospheric pressure metalorganic vapor phase expitaxy (MOVPE) on a (111)A GaAs substrate. Structural parameters such as well and barrier lengths, and the Al fraction in the barriers were accurately determined by high resolution X-ray diffractometry (HRXRD). The PR spectrum exhibits all the possible confined QW transitions between electron and hole sub-bands. The theoretically calculated transition energies are in very close agreement (±1 meV) with those experimentally determined from the PR spectrum even up to the highest possible transition for these wells. From a detailed monolayer (ML) analysis of the various transition energies it is concluded that the QW interfaces have much less than a ±1 ML fluctuation over the 25 periods and that the interfaces are smooth, abrupt and uniform. In addition, photoluminescence (PL) measurements were also used to further assess the optical quality. The PL full width at half maximum (FWHM) is 12.5 meV, which corresponds to less than a ±1 ML fluctuation throughout the 25-period MQW in agreement with the PR analysis. This FWHM is the best value reported to date for AlGaAs/GaAs MQW structures grown on {111} GaAs substrates either by MBE or MOVPE.