Low Temperature LPE Research Articles

Structural and electrical characteristics of InGaAsN layers grown by LPE

Crystallographic and transport properties of nominally undoped and Sn-doped InGaAsN layers grown by low-temperature LPE have been studied and related to the growth conditions.In the case of lattice matching, flat and uniform mirror-like layers of 8–10μm in thickness are obtained. The compositions of the layers under study have been determined by combination of X-ray microanalysis and X-ray diffraction methods to be In0.035Ga0.065As0.086N0.014. The lattice mismatch between layer and substrate Δal/as calculated from X-ray diffraction curves is less than−7×10−4 for all samples. The layers grown at lower epitaxy temperatures exhibit the highest crystalline quality, better lattice match and better homogeneity. This is in good agreement with the results of morphological study by atomic force microscopy which show root mean-square surface roughness of 0.18nm for the best layers.CV and Hall measurements reveal that intentionally undoped InGaAsN layers are n-type with free carrier concentration about one order of magnitude higher in comparison to layers not containing nitrogen and high electron mobility values over 2000cm2/Vs. A dramatic reduction in the free carrier concentration and slightly increase in mobility are observed for Sn-doped InGaAsN layers.

Epitaxial growth of SiC from Al–Si solution reacting with propane gas

A new low-temperature LPE technique has been developed. SiC layers were grown on a Si-face of 6H–SiC substrates from Al–Si solution reacting with propane gas at 1000°C. Morphology of the as-grown surface of the layers changed depending on whether the solution was saturated with Si or not. Based on the observation, two growth modes, corresponding to segregation dominance or surface diffusion dominance, were discussed. The use of off-axis substrates made the growth rate increase remarkably. The thickness reached about 10-μm after 8-h growth. PL measurements revealed that the polytype of the grown layers belongs to a hexagonal group.

Is Al-Si a Good Melt for the Low-Temperature LPE of 4H-SiC?

Is Al-Si a Good Melt for the Low-Temperature LPE of 4H-SiC?

The In–As–Sb phase diagram and LPE growth of InAsSb layers on InAs at extremely low temperatures

A calculation of the In–As–Sb phase diagram in the low-temperature range 300–400°C has been made applying the rare simple solution model. By using the calculated data an extremely low temperature LPE was performed for growing InAs 1− x Sb x layers on InAs substrates at temperatures as low as 300°C. It was shown that high-quality layers can be grown on InAs with x up to 0.26. SEM microprobe compositional analysis and X-ray diffraction analysis confirmed their homogeneity and high crystal quality and the promise of this material for mid-infrared optoelectronic devices.

Low temperature LPE of Hg 1- xCd xTe from Te-rich solution and its effects

Thin films of Hg 1- x Cd x Te were grown on the (111)CdTe substrates by slider liquid phase epitaxy from Te-rich solution in the temperature range from 400 to 500°C. Satisfactory epi-layers were obtained at the temperature as low as 425°C. The low temperature (below 450°C) LPE technique has shown several advantages over the high temperature growth. These are: (i) the residual melt drops can be well drained from the epi-layers after withdrawal from the solution, (ii) the composition gradient of the epilayers is reduced, and (iii) the concentration of mercury vacancies is decreased. The surface morphology of epi-layers is also affected by the change of growth temperature. Large voids were formed quite easily for the growth on (111)A CdTe substrates at low temperatures. However, for the (111)B growth, these voids appeared only occasionally. It was also observed that terraces of a larger spacing were formed for the low temperature growth.

Low temperature LPE growth and photoluminescence of InGaAsP on GaAsP

InGaAsP epilayers were successively grown on a GaAS 0.61P 0.39 substrate at a low growth temperature of 689°C. The characteristic convex relation between X ℓ Ga and X ℓ As was observed. Although the epilayer surfaces were almost mirror-like, somewhat rough surfaces were observed in the epilayers with medium band gaps. The samples with rough surfaces also had wider FWHM's in the photoluminescence spectra. A carrier concentration spike at the substrate-epilayer interface disappeared by lowering the growth temperature from 789 to 689°C. Compositional variation was observed in the epilayers having higher As content, which was due to P atom depletion from the melt.

Low-temperature LPE growth and characterization of InGaAs ternary alloys

InGaAs LPE epilayers have been grown at low temperature, and have been characterized in optical and electrical properties. By measuring the photoluminescence (PL) and also the Raman spectra of the InGaAs epilayer, it has been found that the poor optical properties of the epilayer are due to the influence of low-temperature growth. On the other hand, the electrical properties of mobility and carrier concentration are shown to depend on the sulphur concentrations in the epilayers and do not degrade with low-growth temperature.

The use of alternative solvents for the low-temperature LPE growth of CdTe films

The use of alternative solvents, in particular Bi and In, has been investigated for the LPE growth of CdTe films at temperatures down to 250°C. In comparison with earlier work using Te as a solvent, this approach has several benefits: (i) improved surface topography; (ii) better solution removal; (iii) more abrupt interfaces; (iv) improved electrical properties. SIMS measurements showed that the layers grown from Bi solutions contained ∽0.1 ppma Bi, while those from In solutions contained ∽100 ppma In. Doping experiments with In, Sb and As were performed using Bi as the solvent. Estimated values for the segregation coefficients for growth at 500-400°C were k In∽6×10 -4, k Sb∽10 -4 and k As∽2×10 -3. Layers grown from In solutions showed long minority carrier diffusion lengths ( L h≳20 μm) and very high luminescence efficiency, indicating extremely high quality CdTe.

Surface treatment of GaSb substrate and extremely low temperature LPE growth of AlGaSb

After each process of a chemical etching, heat-cleaning, melt-back, or soaking in HC1, the substrate surface of GaSb was characterized by the Auger electron spectroscopy with a simultaneous Ar sputtering to reveal oxide layer structures. An optimum treatment process of GaSb surfaces for low temperature LPE growth of AlGaSb was established. Uniform growth of epitaxial AlGaSb on GaSb is demonstrated for a wide temperature range(from 500‡C to as low as 250‡C).

LPE growth of InP/InGaAs/InP DH wafers on (100) InP substrates

An InP/InGaAs/InP double heterostructure wafer is grown directly on a (100) InP substrate using very low temperature LPE growth. This crystal exhibits a thin transition layer at a InP-InGaAs interface because of dissolution of the ternary layer.

Characteristics of diffused-stripe InP/InGaAsP/InP lasers emitting around 1.55 µm

Fabrication and lasing characteristics of InGaAsP/InP lasers emitting around 1.55 μm are described. Zn-diffused stripe-geometry lasers with emission wavelengths in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.53-1.60\mu</tex> m range were fabricated from InP/InGaAsP/InP DH epitaxial wafers prepared by a low temperature LPE technique. The dependence of the lasing charaeteristics on the stripe width was examined. The lowest threshold current (≃160 mA under CW operation at 27°C) was obtained for a laser with a 13 μm stripe. CW operation of the laser has been achieved at a heat-sink temperature as high as 53°C. For sufficiently narrow stripe widths ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\simeq6 \mu</tex> m), fundamental-transverse mode and single-longitudinal mode operation was obtained under CW operation. Moreover, the lasers have good high-frequency performance. The lasers showed excellent dynamic properties without waveform distortion under high-frequency (800 Mbits/s) large-signal pulse modulation. The full width at half maximum of the longitudinal mode envelope was approximately 30 Å at 800 Mbits/s.

Gallium antimonide LPE growth from Ga-rich and Sh-rich solutions

Epitaxial layers of undoped p-GaSb were grown from Ga-rich and Sb-rich solutions on (111) and (100) oriented GaSb substrates. The growth temperatures ranged from 330–470°C (Ga solution) and 635–680°C (Sb solution). Different growth results were obtained for the two LPE processes. The layers were characterized by photoluminescence measurements at low temperatures (1.8 K). The highest purity was obtained by low temperature LPE from Ga solutions.