Optical Studies Of Lattice Matched And Strained Gainas/Alinas Single Quantum-Wells

Photoconductivity (PC), photoluminescence (PL), and photoreflectance (PR) have been carried out on In0.52Al0.48As/InxGa1-xAs single quantum wells, in lattice matched and lattice mismatched composition. The unstrained (xIn equals 0.53) and the strained (xIn equals 0.60) samples have been grown by molecular beam epitaxy (MBE), with well thicknesses of 5 nm and 25 nm. Low temperature PL measurements have shown a narrow full width at half maximum (FWHM) for the unstrained samples, indicating a very good interface quality. In strained samples a broadening on the FWHM has been found, indicating a small degradation of the structure quality with the introduction of strain. With the PC and PR measurements we have been able to observe transitions between electron and heavy holes levels (EiHi) up to i equals 5 and also between the first electron and light holes levels (E1L1). We have then calculated the theoretical values of these transitions by solving the Schroedinger equation in a finite square well, using an envelope function approximation, an effective mass approximation, and including the effects of strain on the band structure and on the effective mass. For the lattice matched composition, the best fit is obtained for conduction band offset (Delta) Ec equals 0.50 +/- 0.05 eV, in agreement with the literature. For example, with xIn equals 0.60 composition the best fit is obtained for (Delta) Ec equals 0.55 +/- 0.05 eV, in agreement with theory which predicts that (Delta) Ec increases with indium content.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.