Molecular beam epitaxy of InP-based alloys for long-wavelength vertical cavity lasers

Abstract

In this article we describe the growth, design, and characterization of a 1310nm lattice-matched vertical cavity laser which take advantage of an AlGaAsSb distributed Bragg reflector and AlInGaAs active regions. The molecular beam epitaxial growth for this structure was particularly challenging due to the various III–V alloys used; in particular, the interfaces between them were observed to be a significant source of macroscopic defects and roughness. The AlGaAsSb–InP interface was seen to control the yield and overall quality of device structures, and so was the focus of the crystal growth optimization. InP heat- and current-spreading layers were utilized to offset the thermal and electrical limitations of the AlGaAsSb mirrors; we optimized the defect density and roughness of these epilayers by studying their dependence on growth temperature and P overpressure. Vertical cavity lasers grown using these optimized approaches and incorporating a thin, selectively etched tunnel-junction aperture were fabricated and tested, and demonstrated promising characteristics. Operating temperatures up to 90°C with single-mode power in excess of 1.6mW were observed. Differential quantum efficiency of 64% was seen for our best devices, a record for long-wavelength vertical cavity lasers.

Room temperature electron spin coherence in telecom-wavelength quaternary quantum wells

“…These samples are composed of digital alloys of ternaries ͑Ga 0.47 In 0.53 As and Al 0.48 In 0.52 As, referred to as GaInAs and AlInAs, respectively͒ lattice matched to InP. 10 The sample structure is of the form AlInAs/ ͑AlIn͒ r ͑GaIn͒ 1−r As/ 5 ϫ ͓͑AlIn͒ y ͑GaIn͒ 1−y As/ ͑AlIn͒ x ͑GaIn͒ 1−x As͔ / ͑AlIn͒ y ͑GaIn͒ 1−y As / ͑AlIn͒ r ͑GaIn͒ 1−r As/ AlInAs/ ͑AlIn͒ s ͑GaIn͒ 1−s As/ AlInAs/ InP substrate with r = 0.75 and s = 0.82, shown schematically in Fig. 1͑a͒.…”

“…10,11 We characterize the samples using photoluminescence and measure the electron spin dynamics using pump-probe optical spectroscopy. The electron effective g factors and spin coherence times are found to vary with aluminum alloy concentration from −2.3 to −1.1 and from 50 to 100 ps, respectively.…”

“…Spin-dependent all-optical switching in semiconductor quantum well etalons 8 and spin-dependent ultrafast optical gain modulation in microcavity lasers have been recently demonstrated 9 . In addition, differential quantum efficiency as high as 64% is attainable for all-epitaxially grown telecom-wavelength vertical cavity surface emitting lasers (VCSELs) with InP lattice-matched AlIn-GaAs alloys for quantum well active regions and Al-GaAsSb alloys for highly reflective distributed Bragg reflectors operating above room temperature 10,11 . The possibility of integrating laser sources, optical modulators, and optical switches on a single photonic integrated chip with added functionalities based on spin degrees of freedom makes AlInGaAs alloys ideal candidates for spintronics.…”

“…In this letter, we present room temperature measurements of the electron spin coherence times and effective g-factors in AlInGaAs multiple quantum wells, which are optimized active regions of VCSELs with wavelengths in the range 1.26 − 1.53 µm designed for optical telecommunication applications 10,11 . We characterize the samples using photoluminescence and measure the electron spin dynamics using pump-probe optical spectroscopy.…”

“…Our samples are comprised of a set of quaternary alloy AlInGaAs multiple quantum wells grown using digital alloy molecular beam epitaxy. These samples are composed of digital alloys of ternaries (Ga 0.47 In 0.53 As and Al 0.48 In 0.52 As, referred to as GaInAs and AlInAs, respectively) lattice-matched to InP 10 .…”