Single-step Liquid Phase Epitaxy Research Articles

Layered Growth of Lattice-Mismatched Ga x In1−x P on GaP Substrates by Liquid Phase Epitaxy

We report layered growth of Ga x In1−x P on GaP substrates using single-step liquid phase epitaxy (LPE) with a Sn-based melt when the lattice mismatch is greater than 0.4 % (x < 0.95). Compositional control was observed by (1) varying the cooling rate and (2) changing the melt-back temperature at the beginning of the growth. Possible growth mechanisms are proposed to explain the principles of both approaches of compositional control. Smooth epilayers have been observed. High resolution x-ray diffraction was used to characterize the composition of the epilayers, and room temperature photoluminescence was reported for one of the samples with the composition of x = 0.11. Plan-view TEM measurements revealed threading dislocation densities on the order of 108 cm−2 in the upper regions of the Ga x In1−x P epilayers. In contrast, when using In-based melts, LPE of Ga x In1−x P on GaP (100) substrates exhibited island growth at large misfits, whereas edge growth dominated when using GaP (111B) substrates under equivalent growth conditions.

Single-step growth of InGaAsP/InP laser array on patterned InP substrate

Arrays of five InGaAsP/InP single mode junction-defined buried stripe heterostructure lasers are described. The laser arrays were grown on multi-channeled InP substrate by single-step liquid phase epitaxy . The buried double heterostructure and the lateral current confining structure were formed in the same growth process. InGaAsP layer growth is dominated by the preferred orientation, with (1 0 0) growth favored over other directions. As a result of low-temperature single-step growth, the device yield is high. These laser arrays are characterized by output power close to 0.6 W , high quantum efficiency, symmetrical far-field patterns and excellent linearity of the light–current curve. Stable single transverse mode operation obtained up to 600 mW emitted power.

Channelled substrate window twin stripe GaAs/GaAIAs visible lasers: fabrication and steady-state analysis

GaAs/GaAIAs high-power window stripe lasers have been developed with a uniform active layer in the region adjacent to the device facets and with a curved active layer in the central region. A single-step liquid-phase epitaxy growth is used in the fabrication process to form two internal lateral current paths, so allowing for a very simple fabrication process. The optical coupling between the two stimulation emission regions reduces the beam divergence. The steady-state analysis of such a laser structure, including heating effects, agrees well with experimental results.

1.55 μm high-power large optical cavity lasers

A high-power 1.55 μm large optical cavity (LOC) laser structure is successfully prepared for the first time by reasonably designing its configuration and by using a proper single step liquid phase epitaxy (LPE) so as to realize lasers with peak output power higher than 2 W per facet in pulsed operation at room temperature. The devices are also characterized by their lower threshold current ( Jth≤2.7 KA/cm2 for broad area contact structure) and high-temperature stability (T0≊130 K). At the same time they are of long-lived operation and are an ideal source of light in this spectral region.

Room-temperature CW operation of λ = 1.55 μm InGaAsP/InP ITG-DFB-BCRW lasers with contacted surface grating

The structure and fabrication of the first quasi-index-guided DFB laser with a contacted surface grating is described. This device is grown by a standard single step liquid phase epitaxy process without a corrugation overgrowth. Room-temperature CW-DFB-laser operation with a threshold current of 75 mA is reported. A sidemode-suppression ratio of 35 dB is achieved.

Trapezoidal channeled substrate inner stripe phase-locked semiconductor laser arrays

A novel type of trapezoidal channeled substrate inner stripe diode laser array grown by single-step liquid-phase epitaxy was designed and fabricated. A six-element array with evanescent wave coupling, as well as leaky wave coupling, shows a continuous-wave threshold current of 170 mA and a pulsed peak power over 675 mW per facet without a coating. A clean single-lobe far-field pattern of beam width 2.4° is obtained.

Low threshold 1.3-μm InGaAsP/InP lasers prepared by a single-step liquid-phase epitaxy

A novel approach to form low threshold laser structures, similar to existing mass-transported lasers but without the second regrowth step, is described. The laser has comparable performance in threshold current and quantum efficiency to more conventional buried heterostructure lasers made with a two-step process. Because of the simplicity in fabrication and its reduced parasitic capacitance it has the potential to be low cost and to have high modulation bandwidth.

Cd diffused mesa-substrate buried heterostructure InGaAsP/InP laser

A new type of buried heterostructure InGaAsP/InP lasers grown by a single-step liquid phase epitaxy on Cd diffused mesa substrate is described. These lasers exhibit excellent current and optical confinement. Threshold currents as low as 15 mA are achieved for a laser with a 2-μm-wide active region.

High-power, low-threshold, single-mode GaInAsP/InP laser by low-temperature, single-step liquid phase epitaxy

A GaInAsP/InP laser (λg=1.3 μm) on grooved substrate with a lens-shaped active layer, in which the current blocking junction is grown exclusively outside of the groove, has been fabricated by single-step liquid phase epitaxy. This technique is based on the preferential growth effects of InP and GaInAsP on the (100) oriented substrate with [011̄] directed grooves. Under cw operation, low threshold current (38 mA), high output power (40 mW/facet), and high external differential quantum efficiency (56%) are accomplished; fundamental transverse mode operation up to an output of 30 mW/facet is verified. These successful characteristics are realized by the introduction of the inner current confining layer.

InGaAsP/InP undercut mesa laser with planar polyimide passivation

An undercut mesa laser is fabricated on an n+-InP substrate using a single step liquid phase epitaxy growth process and a planar structure is obtained by using a polyimide filling layer. The lasers operate at fundamental transverse mode due to a scattering loss mechanism. Threshold currents of 18 mA and stable single transverse mode operating at high currents are obtained.

High power single mode InGaAsP lasers fabricated by single step liquid phase epitaxy

Lasing properties of an InGaAsP (λ=1.3 μm) crescent-shaped buried heterostructure laser are presented. The structure was grown by single step liquid phase epitaxy on a mesa substrate. High output power in pulsed operation (150 mW/facet) and high external differential quantum efficiency (60%) are realized in this structure even though there is no special layer for current blocking. Fundamental mode operation up to a power level of 30 mW/facet is found. These characteristics are attributed to the effect of the mesa on current flow and they demonstrate the importance of substrate topography on laser performance.

1.5 μm GaInAsP/InP distributed Bragg reflector lasers with built-in optical waveguide

Room-temperature operation of distributed Bragg reflector (DBR) lasers emitting at 1.5 μm is reported. The diode was fabricated by conventional techniques and has a simple configuration with a built-in waveguide grown by single-step liquid-phase epitaxy. Single-longitudinal-mode oscillation at 1.504-1.505 μm was obtained at temperatures between -10°C and 5°C with 310-360 mA threshold current.

High-T 0 low-threshold crescent InGaAsP mesa-substrate buried-heterojunction lasers

A crescent-shape mesa-substrate buried-heterostructure (CMSB) InGaAsP laser (? = 1.3 ?m) was grown by a single-step liquid phase epitaxy. Threshold current as low as 25 mA with 200 ?m cavity length under pulse operation and linear light/current characteristics up to five times Ith were obtained. T0 as high as 97°C was achieved for the first time for quaternary lasers. High output power, ~15 mW/facet, has been realised.

Transverse mode stabilized AlGaAs/GaAs plano-convex waveguide laser made by a single-step liquid phase epitaxy

A new laser structure, the plano-convex waveguide (PCW) laser is described. A thickness-varied waveguide layer used for transverse mode stabilization was formed adjacent to the planar active layer. The laser structure was fabricated by a single-step liquid phase epitaxial growth on a grooved substrate. With pulsed injection, stable fundamental transverse mode operation was observed up to 3.5 times threshold current, where power output was 36 mW/facet. At zero dc bias, single longitudinal mode was attained after 10 ns of the leading edge of the optical pulse. Far-field beam divergences of about 10° and 50° were obtained in directions parallel and perpendicular to the junction plane, respectively.