-oriented (indium,gallium)arsenic/(aluminum,gallium)arsenic quantum well structures and their optical and strain-induced piezoelectric and pyroelectric properties

This thesis concentrates on a comprehensive evaluation and determination of the physical properties of ⟨111⟩-oriented (In,Ga)As/(Al,Ga)As quantum-well (QW) structures. Especially, the emphasis was placed on a detailed investigation of the piezoelectric (PE) and pyroelectric properties of strained InGaAs layers in InGaAs/GaAs QW structures.; The [111]A-oriented (In,Ga)As/(Al,Ga)As QW structures were grown by metalorganic vapor phase epitaxy (MOVPE) and were analyzed by a combination of various optical and structural measurement techniques. The interfacial abruptness for QWs was quantitatively determined by a monolayer (ML) analysis which consists in a comparison between the experimental transition energies, particularly for high-order transitions, obtained from photoreflectance (PR) spectra and the theoretical transition energies calculated for a varying well width. An interpretation of the photoluminescence linewidths and the PR broadening parameters allowed a quantitative evaluation of interfacial roughness. These methods demonstrated the high structural quality of unstrained GaAs/AlGaAs and highly strained InGaAs/GaAs QW, P-I-N, and N-I-P structures and confirmed the achievement of 1–2 ML heterointerfaces.; We quantified the values of key electronic parameters appropriate for [111]-oriented QWs, such as bandgap offsets and heavy-hole effective mass which were previously not well established, by comparing the PR transitions with theoretical transition energies computed for a range of values of each electronic parameter. Also, from an analysis of the temperature dependence of the PR broadening parameters based on the Bose-Einstein phonon-coupling model we determined for the first time the optical phonon energy and the electron-phonon coupling energy for [111]-oriented InGaAs/GaAs QW structures.; Finally, either from an analysis of Franz-Keldysh oscillations or from a theoretical interpretation of optical measurements in conjunction with a simulation of QWs, we obtained the temperature dependence of the PE constant e₁₄ for strained In_xGa_1−xAs (x = 0.12–0.30) layers in InGaAs/GaAs QW structures grown on (111)A and (111)B GaAs substrates by MOVPE and molecular beam epitaxy, respectively. It was observed that e₁₄ increases linearly with temperature over the range of 11–300 K, from which the strain-induced pyroelectric coefficient was determined to increase from (4.5 ± 0.2) × 10−7 C/m2K to (23.5 ± 0.7) × 10−7 C/m2K for In fractions of x = 0.12 and x = 0.30, respectively, for the first time to my knowledge.