Yu Zhu Gao

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 54,400cm(2)/Vs is the best result, so far, for the InAsSb materials with cutoff wavelength of 8-12 mum 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

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 InAs_(0.04)Sb_(0.96) epilayers with a cutoff wavelength of 12 μm was performed using Van der Pauw measurements.The temperature dependence of the electrical properties was measured.An electron mobility of 6×10~4 cm~2/Vs with a carrier density of 2.3×10~(16) cm~(-3) at 300 K,and an electron mobility of 1×10~5 cm~2/Vs with a carrier density of 1×10~(15) cm~(-3) at 200 K have been obtained in the experiments.Different behaviors of the electrical properties of samples grown using graphite and fused-silicon boats,were observed 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 of the sample grown using a graphite boat.

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.

Optical Properties of InAsSb Single Crystals with Cutoff Wavelengths of 8–12 µm Grown by Melt-Epitaxy

The transmittance spectra of melt epitaxiy (ME)-grown InAsSb single crystals with cutoff wavelengths of 8–12 µm were measured and calculated under the assumption of a microscopic composition distribution function. A good agreement between the experimental and theoretical transmittance spectra was obtained. The results indicate that a microscopic composition distribution inhomogeneity exists in long-wavelength InAsSb epilayers with different compositions, which may be related to the energy band gap narrowing of this InAsSb.

Room-Temperature Mid-Infrared Light-Emitting Diodes from Liquid-Phase Epitaxial InAs/InAs0.89Sb0.11/InAs0.80P0.12Sb0.08 Heterostructures

Light-emitting diodes (LEDs) in the 3 to 5 µm wavelength range have been fabricated from InAs/InAsSb/InAsPSb heterostructures grown by liquid-phase epitaxy (LPE) between 520 and 500°C. Temperature dependence of the performance for the LEDs was studied using a Fourier transform infrared (FTIR) measurement system with double modulation. Room-temperature operation of LEDs was realized. Under a peak current of 5 A (2% duty cycle), the output powers of the diodes were between 150 and 500 µW indicating their potential applications for CO2 and CO gas sensors.

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.

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.

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 pm 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 10 4 cm 2 /Vs and a carrier density of 8 x 10 15 cm -3 have been obtained for an InAs 0.04 Sb 0.96 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.

Light-Emitting Diodes with a Peak Wavelength of 5.38 µm from Liquid-Phase Epitaxial Ga0.1In0.9Sb/InSb Heterostructures

Light-emitting diodes (LEDs) with a peak wavelength of 5.38 µm were fabricated for the first time from n+-Ga0.1In0.9Sb/n-InSb/p+-Ga0.1In0.9Sb heterostructures grown by liquid-phase epitaxy (LPE) between 360 and 350°C. The device performance was studied using a Fourier transform infrared (FTIR) measurement system. At average drive currents of 400 mA at 15 K and 300 mA at 77 K, the output powers of more than 3 mW and 200 µW were respectively obtained, indicating potential applications as a light source for NO gas sensors.