Melt Epitaxy Research Articles

Improved performance of InAs0.07Sb0.93 photoconductors operating at room temperature

In this study, the improvement of detectivities D* at the wavelength of 8 and 9μm of InAs0.07Sb0.93 photoconductors are provided. InAs0.07Sb0.93, InAs0.05Sb0.95 and InAs0.03Sb0.97 thick epilayers were grown on InAs substrates by melt epitaxy (ME). The photoconductors were fabricated based on the epilayers. Ge immersion lenses were set on the devices. At room temperature, the photoresponse wavelength range was 2–10μm. The peak detectivities Dλp* (6.5 μm, 800) were larger than 1.0×109cmHz1/2W−1. The detectivities D* at 8 and 9 μmof InAs0.07Sb0.93 detectors were raised to 5.01×108cmHz1/2W−1 and 2.92×108cmHz1/2W−1 respectively, which are higher than that of InAs0.05Sb0.95 and InAs0.03Sb0.97 detectors. It benefits from arsenic composition increasing in the epilayers.

Uncooled InAs0.09Sb0.91 photoconductors with cutoff wave-length extended to 11.5 μm

Uncooled InAsSb photoconductors were fabricated. The photoconductors were based on InAs0.05Sb0.95 and InAs0.09Sb0.91 thick epilayers grown on InAs substrates by melt epitaxy (ME). Ge immersion lenses were set on the photoconductors. The cutoff wavelength of InAs0.09Sb0.91 detectors is obviously extended to 11.5 µm, and that of InAs0.05Sb0.95 detectors is 8.3 µm. At room temperature, the peak detectivity of D λp* at wavelength of 6.8 µm and modulation frequency of 1 200 Hz is 1.08×109 cm·Hz1/2·W−1 for InAs0.09Sb0.91 photoconductors, the detectivity D* at wavelength of 9 µm is 7.56×108 cm·Hz1/2·W−1, and that at 11 µm is 3.92×108 cm·Hz1/2·W−1. The detectivity of InAs0.09Sb0.91 detectors at the wavelengths longer than 9 µm is about one order of magnitude higher than that of InAs0.05Sb0.95 detectors, which rises from the increase of arsenic (As) composition in InAs0.09Sb0.91 materials.

InAsSb thick epilayers applied to long wavelength photoconductors

InAs0.052Sb0.948 epilayers with cutoff wavelengths longer than 8 μm were successfully grown on InAs substrates using melt epitaxy (ME). Scanning electron microscopy observations show that the interface between the epilayers and substrates is flat, indicating the good quality of the epilayers, and the thickness of the epilayers is 40 μm. Photoconductors were fabricated using InAs0.052Sb0.948 thick epilayers grown by ME. Ge optical lenses were set on the photoconductors. At room temperature, the photoresponse wavelength range was 2–10 μm. The peak detectivity D λp * reached 5.4 × 109 cm·Hz1/2·W−1 for the immersed detectors. The detectivity D* was 9.3 × 108 and 1.3 × 108 cm·Hz1/2·W−1 at the wavelength of 8 and 9 μm, respectively. The good performance of the uncooled InAsSb detectors was experimentally validated.

InAsSb Single Crystals and Photoconductors with Cutoff Wavelengths Longer than 8 µm

High sensitivity uncooled InAsSb photoconductors with cutoff wavelengths longer than 8 mm were experimentally validated. The detectors were fabricated using InAs0.052Sb0.948 and InAs0.023Sb0.977 single crystals grown on InAs substrates by melt epitaxy (ME). The thickness of the epilayers was 50 mm. Ge optical lenses were set on the photoconductors. At room temperature, the photoresponse wavelength range was 2-10 m. Peak detectivity Dλp* (6.5 mm, 1200 Hz) reached 5.4 × 109 cm Hz1/2 W-1 for InAs0.052Sb0.948 immersed detectors. The detectivity D* was 9.3 × 108 and 1.3 × 108 cm Hz1/2 W-1 at the wavelength of 8 and 9 mm respectively. The good performances of InAsSb detectors indicate the possible detection applications

Uncooled InAsSb Photoconductors with Long Wavelength

High-sensitivity uncooled InAsSb photoconductors with long wavelength were successfully fabricated. The detectors are based on InAsSb epilayers with the thickness of 100 µm grown on InAs substrates by melt epitaxy (ME). Si optical lenses were set on the photoconductors without any antireflective coatings. At room temperature, the peak detectivity Dλp* (6.5 µm, 1200) reaches 5.3 ×109 cm Hz1/2 W-1 for InAsSb immersion photoconductors. The detectivity D* at the wavelength of 8 µm is 1.5 ×108 cm Hz1/2 W-1, and that at 9 µm is 1.0 ×107 cm Hz1/2 W-1. The excellent performance of the detectors indicates the potential applications for infrared (IR) detection and imaging at room temperature.

High-Sensitivity InAsSb Photoconductors with a Response Wavelength Range of 2–9 µm Operated at Room Temperature

InAsSb immersion photoconductors with a response wavelength range of 2–9 µm operated at room temperature were reported. The detectors are based on InAsSb single crystals grown on InAs substrates by melt epitaxy (ME). Van der Pauw measurements showed that the 300 K electron mobilities of InAsSb materials are higher than 5×104 cm2 V-1 s-1 with carrier densities of (1–3)×1016 cm-3. The photoconductors were measured using a standard blackbody source at a temperature of 500 K and a modulation frequency of 800 Hz under an applied bias current of 10 mA. At 293 K, the blackbody detectivity Dbb* (500 K, 800) reaches (2–6)×108 cm Hz1/2 W-1, indicating the high sensitivity of the detectors and their potential detection applications.

Spectroscopic ellipsometry of anodized layer on single crystal InAsSb layer grown by melt epitaxy

AbstractAnodized layers on InAsSb, InSb, and InAs surfaces are characterized using phase modulation spectroscopic ellipsometry in a wide spectral range from 0.6 to 6.5 eV. Single crystal InAs0.04Sb0.94 layer was grown using melt‐epitaxy (ME). Optical properties of anodized layer prepared on InAsSb single crystal are compared with those on pure single crystals of InAs and InSb. Ellipsometric spectra of were fitted to the Tauc‐Lorentz model describing the anodizing layer optical functions. Clear tendency of ultraviolet shift of the band gap energy with decreasing antimony content is observed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrical Properties of Melt-Epitaxy-Grown InAs0.04Sb0.96 Layers with Cutoff Wavelength of 12 µm

A study of the electrical properties of melt epitaxy (ME)-grown InAs0.04Sb0.96/InAs epilayers with a cutoff wavelength of 12 µm was performed. From the measured temperature dependence of the electrical properties, a peak electron mobility of 100,000 cm2/V·s with a carrier density of 1×1015 cm-3 at 200 K, and an electron mobility of 60000 cm2/V·s with a carrier density of 2.3×1016 cm-3 at 300 K have been obtained for the first time. The different behaviors of the electrical properties were observed for samples grown using graphite and fused-silicon boats, and were analyzed in terms of their scattering mechanism. The results showed that ionized impurity scattering is the dominant process at low temperatures for all the samples. Polar optical phonon scattering governs electron mobility at high temperature. C contamination has significant influence on the electron mobility below 200 K for the sample grown using a graphite boat.

InNAsSb Single Crystals with Cutoff Wavelength of 11–13.5 µm Grown by Melt Epitaxy

We grew, for the first time, InNAsSb single crystals with a room temperature cutoff wavelength of 11–13.5 µm on (100) InAs substrates by melt epitaxy (ME). The crystals were characterized using X-ray diffraction, electron-probe microanalysis (EPMA), temperature-dependent transmittance and Van der Pauw measurements. An obvious redshift of cutoff wavelength was observed with increasing N concentration from 13 to 19% in the epilayers. The cutoff wavelength varies from 12.5 to 8.9 µm in the temperature range from 300 to 77 K. The thick epilayers show a good macroscopic homogeneity of the composition. An electron mobility of 55,800 cm2/Vs with a carrier density of 1.08×1016 cm-3 was obtained at 77 K, indicating possible applications for infrared photodevices.

Improved purity of long-wavelength InAsSb epilayers grown by melt epitaxy in fused silica boats

In this study, we first present the process of the melt epitaxial (ME) growth method, and the improvement of low-temperature electron mobility of the long-wavelength InAsSb epilayers grown by ME in a fused silica boat. The electrical properties were investigated by van der Pauw measurement at 300 and 77 K. It is seen that the electron mobility of the InAsSb samples grown by graphite boat decreased from 55,700 to 26,600 cm 2/V s when the temperature was reduced from 300 to 77 K, while for the samples grown by fused silica boat, the electron mobility increased from 52,600 at 300 K to 54,400 cm 2/V s at 77 K. The electron mobility of 54,400 cm 2/V s is the best result, so far, for the InAsSb materials with cutoff wavelength of 8–12 μm at 77 K. This may be attributed to the reduction of the carbon contamination by using a fused silica boat instead of a graphite boat.

High purity InxGa1−xSb single crystals with cutoff wavelength of 7–8 µm grown by melt epitaxy

For the first time, InGaSb single crystals with a cutoff wavelength of 7–8 µm were successfully grown on GaAs substrates by a new growth technique named melt epitaxy. The band gap of InGaSb layers obviously narrowed compared with those with the same compositions grown by ordinary methods and the longest cutoff wavelength reached 8.3 µm. High electron mobility of 8.05×104 cm2/Vs and low carrier density of 1×1015 cm−3 at 77 K were obtained indicating high purity of InGaSb epilayers.

The Improvement of Low Temperature Mobility of InAs0.04Sb0.96 Epilayers with Cut Off Wavelength of 12.5 μm by Annealing

We have reported narrowed band gap InAsSb single crystals with cut off wavelength of 8-12 μm grown by a new method of Melt Epitaxy (ME) (GAO et al. 1999). In this paper, we firstly present the improvement of low temperature mobility of the InAsSb epilayers with cut off wavelength of 12.5 μm by annealing treatment. The electrical properties were investigated by Van der Pauw measurements at 300 K and 77 K. After an annealing treatment for 11 hours, an electron mobility of 4.83 x 104 cm2/Vs and a carrier density of 8 x 1015 cm-3 have been obtained for an InAs0.04Sb0.96 epilayer at 77 K. This is the best result so far for the InAsSb materials with cut off wavelength of 8-12 μm. The mechanism of the improvement of the electrical properties for this material after annealing treatment was studied by observing the etch pits on the surface of the sample before and after heat treatments.

Germanium- and Zinc-Doped P-type InAsSb Single Crystals with a Cutoff Wavelength of 12.5 µm

We grew germanium (Ge)- and zinc (Zn)-doped p-type InAs0.04Sb0.96 epilayers with a cutoff wavelength of 12.5 µm on n-InAs substrates by melt epitaxy (ME), and undertook a study of the properties of Ge-doped long-wavelength p-InAsSb epilayers. The quality of the epilayers was evaluated by transmittance, electroprobe microanalysis (EPMA) and Van der Pauw measurements. The results showed that the cutoff wavelength of the InAsSb epilayers with different levels of Ge doping showed no significant changes when the composition of the epilayers was kept constant. The Ge distribution, both on the surface and along the growth direction of the epilayer, is rather homogeneous. A maximum hole mobility of 1120 cm2/Vs with a carrier density of +9.18 ×1016 cm-3 at 77 K was achieved in a Ge-doped p-InAsSb epilayer. However, in the case of a Zn-doped epilayer, a hole mobility of 860 cm2/Vs with a carrier density of +2.48 ×1017 cm-3 was obtained at 77 K.

Liquid phase epitaxy processes for GaP led's

The first utilization of LPE for large scale production is for GaP light emitting diodes (LED's). In this paper we compare various approaches to multislice LPE and techniques of junction formation from the standpoint of LED fabriaction. A new technique involving a combination of thin melt epitaxy and vapor doping is emphasized as a method which is compatible with economic large scale production and state-of-the-art device performance. A detailed account of the growth procedure, surface quality and device performance is presented for a laboratory-prototype mass production system for green LED material.