Tensile-strained InGaP Research Articles

High-Q Trampoline Resonators from Strained Crystalline InGaP for Integrated Free-Space Optomechanics.

Nanomechanical resonators realized from tensile-strained materials reach ultralow mechanical dissipation in the kHz to MHz frequency range. Tensile-strained crystalline materials that are compatible with epitaxial growth of heterostructures would thereby at the same time allow realizing monolithic free-space optomechanical devices, which benefit from stability, ultrasmall mode volumes, and scalability. In our work, we demonstrate nanomechanical string and trampoline resonators made from tensile-strained InGaP, which is a crystalline material that is epitaxially grown on an AlGaAs heterostructure. We characterize the mechanical properties of suspended InGaP nanostrings, such as anisotropic stress, yield strength, and intrinsic quality factor. We find that the latter degrades over time. We reach mechanical quality factors surpassing 107 at room temperature with a Q·f product as high as 7 × 1011Hz with trampoline-shaped resonators. The trampoline is patterned with a photonic crystal to engineer its out-of-plane reflectivity, desired for efficient signal transduction of mechanical motion to light.

High-Performance Visible Semiconductor Lasers Operating at 630 nm

A tensile-strained InGaP quantum-well laser structure operating around 630 nm has been designed. The structure offers low threshold current and beam divergence (19° full-width at half-maximum (FWHM) or 34° at 1/e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) simultaneously by incorporating a V-profile layer within the waveguide. Single-mode lasers (630 nm) were fabricated and tested. The threshold current for coated 1-mm-long and 3-m-wide ridge lasers is only 30 mA, and the slope efficiency is 1.04 W/A. This level of performance makes the lasers ideal for display applications.

Polarization response of quantum-confined structures using edge-photovoltage spectroscopy

We propose a method to obtain the ratio of the fundamental TE/TM optical response of a quantum-confined system from the measurement of the polarization dependence of the edge photovoltage spectrum by correcting for polarization-dependent features of the experimental system. When applied to compressive- and tensile-strained InGaP quantum well structures, the results are in excellent agreement with known ratios of the band-edge matrix elements. The method will be of a particular value in the study of quantum dot systems.

Tunneling injection quantum-dot lasers with polarization-dependent photon-mediated carrier redistribution and gain narrowing

A theoretical and experimental study of a particular transverse-electric (TE) mode lasing mechanism of a tunneling injection InP quantum-dot (QD) laser is reported. In the experiment, the TE mode lasing action takes place at the first excited state of InP biaxially compressively strained QDs. This QD state is coupled to the ground state of two tensile-strained InGaP quantum wells (QWs) although the tensile-strained QW structure favors the transverse-magnetic (TM) polarization light emission. The measured TE and TM modal gain spectra show a typical QW gain evolution behavior at low injection currents, which can be theoretically modeled by the quasi-equilibrium of carrier distribution. When the injection current is increased near threshold, a TE gain narrowing and a simultaneous TM gain pinning are observed in the measured modal gain spectra, which cannot be explained via the quasi-equilibrium model. We propose a polarization-dependent photon-mediated carrier redistribution in the QD-coupled-QW structure to explain this TE and TM gain evolution behavior. When the injection current is just below threshold, the strong carrier depletion via stimulated emission due to coupling between the InP QD and InGaP QW states plays an important role in carrier redistribution, which depends on the optical transition energy and polarization. This concept of the polarization-dependent photon-mediated carrier redistribution explains the TE gain narrowing and TM gain pinning behavior. In addition, a coupled rate equation model is established, and the calculated polarization power ratio based on the coupled rate equations explains the experimental observation.

Tunneling Injection Quantum-Dot Lasers

ABSTRACTWe investigate a tunneling injection InP quantum-dot (QD) laser theoretically and experimentally. The device consists of a single compressively strained InP QD layer coupled closely to two tensile strained InGaP quantum wells (QWs). While most tensile strained QW lasers in this wavelength (red) range lase in the transverse-magnetic (TM) polarization, our QD laser lases in the transverse-electric (TE) polarization from the first excited state of the compressively strained QDs, which is coupled to the ground state of the tensile-strained InGaP QWs. When we measure TE and TM modal gain spectra, a typical QW gain evolution behavior is observed at low injection currents, which can be theoretically explained by the quasi-equilibrium of carrier distribution. When the injection current is increased near threshold, a TE gain narrowing and a simultaneous TM gain pinning are observed in the measured modal gain spectra, which cannot be explained via the quasi-equilibrium model. We propose a polarization-dependent photon-mediated carrier re-distribution in the QD-coupled-QW structure to explain this TE and TM gain evolution behavior. When the injection current is just below threshold, the strong carrier depletion via stimulated emission due to coupling between the InP QD and InGaP QW states plays an important role in carrier re-distribution, which depends on the optical transition energy and polarization. This polarization-dependent photon-mediated carrier re-distribution explains the TE gain narrowing and TM gain pinning behavior. To quantitatively demonstrate the photon-mediated carrier re-distribution near the threshold current, a set of coupled rate equations are solved taking into account the polarization-dependent stimulated emission processes. The calculated polarization power ratio based on the coupled rate equations explains the experimental observations.

Nanoengineering of lateral strain modulation in quantum well heterostructures

We have developed a method to design a lateral band-gap modulation in a quantum well heterostructure. The lateral strain variation is induced by patterning of a stressor layer grown on top of a single quantum well which itself is not patterned. The three-dimensional (3D) strain distribution within the lateral nanostructure is calculated using linear elasticity theory applying a finite element technique. Based on the deformation potential approach the calculated strain distribution is translated into a local variation of the band-gap energy. Using a given vertical layer structure we are able to optimize the geometrical parameters to provide a nanostructure with maximum lateral band-gap variation. Experimentally such a structure was realized by etching a surface grating into a tensile-strained InGaP stressor layer grown on top of a compressively strained InGaAs-single quantum well. The achieved 3D strain distribution and the induced band-gap variation are successfully probed by x-ray grazing incidence diffraction and low-temperature photoluminescence measurements, respectively.

The influence of InGaP barrier layer on the characteristics of 1.3 μm strain-compensated multiquantum-well InAsP/InP/InGaP laser diodes

In this article, we report the influence of InGaP barrier layer on the performance of 1.3 μm InAsP/InP/InGaP strain-compensated multiquantum-well (SCMQW) laser diodes (LDs) grown by metalorganic chemical vapor deposition. Sharp satellite peaks with narrow width in double-crystal X-ray diffraction measurements and abrupt interface in secondary ion mass spectrometry analyses are observed, indicating that a good epitaxial-layer quality can be obtained through the use of strain-compensation coupled by InGaP barrier layers. By increasing InGaP barrier thickness to above 6 nm, a redshift of the photoluminescence peak is observed in the (1 0 0)-oriented strained layers. It is probably attributed to redistribution across the samples of the huge built-in electric field induced by the piezoelectric effect. The threshold current of InAsP/InP/InGaP SCMQW ridge-waveguide LDs decreases from 78.8 to 33.8 mA through the employ of tensile-strained InGaP barrier layer and the lasing wavelength is 1.307 μm under 44 mA. In addition, the experimental data of broad-area LDs for the InAsP/InP strained multiquantum-well and InAsP/InP/InGaP SCMQW structures are compared in detail.

2 W reliable operation in 50 µm-wide InGaAsP/InGaP/AlGaAs(λ = 810 nm) SQW diode lasers with tensile-strained InGaP barriers

A new InGaAsP/InGaP/AlGaAs (/spl lambda/=810 nm) laser with tensile-strained InGaP barriers, broad waveguide structure and current blocking region near the facet is reported. 2W continuous wave operation over 2000 h from a 50 /spl mu/m aperture was achieved.

1 W CW reliable λ = 730 nm aluminium-freeactive layer diode laser

1 W continuous wave (CW) reliable operation (/spl sim/1000 h) in large transverse spot-size (d/T=0.55 /spl mu/m), compressively strained, InGaAsP (/spl lambda/=0.73 /spl mu/m)-active region diode lasers is demonstrated. The use of tensile-strained InGaP barrier layers provides strain-compensation and results in a weak temperature sensitivity for the threshold current (T/sub 0/=125 K) and external differential quantum efficiency (T/sub 1/=410 K).

High temperature (77 °C) operation of 634 nm InGaAlP multiquantum-well laser diodes with tensile-strained quantum wells

634 nm InGaAlP multiquantum-well (MQW) laser diodes, with tensile-strained InGaP well layers, have been investigated. A threshold current as low as 59 mA was achieved, at 20 °C, under continuous wave (cw) operation. These MQW laser diodes were able to operate up to temperatures as high as 77 °C under cw conditions. This maximum cw operation temperature is the highest ever reported for 634 nm laser diodes. These MQW laser diodes have shown stable cw operation over 2000 h at an output power of 3 mW, at an ambient temperature of 50 °C.