K.W Mah

TRANSPORT AND PHOTOLUMINESCENCE OF SILICON-DOPED GAINP GROWN BY A VALVED PHOSPHORUS CRACKER CELL IN SOLID SOURCE MOLECULAR BEAM EPITAXY

We report the transport and photoluminescence (PL) properties of silicon-doped GaInP layers grown on GaAs (100) substrate using a valved phosphorus cracker cell in solid source molecular beam epitaxy. Within the range of silicon (Si) effusion cell temperature investigated (900–1200 °C), the highest electron concentration obtained was 7.7×1018 and 3.2×1018 cm−3 at room temperature and 77 K, respectively. The concentration decreased with further increase in the silicon cell temperature. The Hall mobility at 300 K varied from 356 to 1720 cm2/V s within the range of electron concentration measured (4.5×1016–7.7×1018 cm−3). Except for the sample grown at the highest silicon cell temperature (1200 °C), the PL spectrum of other samples showed a dominant peak attributed to Si donor-to-band transition (D–B), which shifted to higher energy following an increase in the electron concentration. This phenomenon was attributed to the Burstein–Moss effect. The blueshift of the (D–B) transition peak at increasing temperat...

The effect of elastic strain on the optical properties of InGaP/GaAs grown using a valved phosphorus cracker cell in solid source MBE

We report the effect of elastic strain on the optical properties of In1−xGaxP grown using a valved phosphorus cracker cell in solid source molecular beam epitaxy (SSMBE). Sample characterization was carried out using photoluminescence (PL) and double-axis X-ray diffraction (XRD). All the In1−xGaxP epilayers prepared in this study are gallium-rich (tensile strained) with composition x in the range of 0.516<x<0.559. The unstrained plot of the band-gap as a function of composition x was deduced from the tensile-strained data obtained experimentally by assuming that the valence band splitting is due only to biaxial elastic strain. The unstrained plot of band-gap vs. composition x for our MBE-grown samples was about 10 meV and 20 meV lower than those reported for samples grown by organometallic vapour phase epitaxy (OMVPE) and liquid phase epitaxy (LPE) techniques, respectively. The photoluminescence (PL) full width at half-maximum (FWHM) of the InGaP samples was higher as the composition x increases due to an increase in the lattice mismatch. Compared to other growth techniques involving the use of higher substrate temperature, InGaP of comparable optical quality can be grown using the valved phosphorus cracker cell SSMBE technique.

Electrical and optical properties of InP grown by molecular beam epitaxy using a valved phosphorus cracker cell

Abstract We report the molecular beam epitaxial (MBE) growth of high quality epitaxial indium phosphide (InP) using a valved phosphorus cracker cell over a wide range of V/III flux ratio (1.2–9.3) and substrate temperature (360°C to 500°C). The as-grown epitaxial InP on InP (100) substrate was n-type, with a background electron concentration and mobility which varied according to the V/III flux ratio and substrate temperature ( T s ). Using a cracking zone temperature ( T cr ) of 850°C, the highest electron mobility at 77 K of 40 900 cm 2 /Vs was achieved at a V/III flux ratio of 2.3 at a substrate temperature of 440°C. The corresponding background electron concentration at 77 K was the lowest at 1.74×10 15 cm −3 . The photoluminescence (PL) full-width at half maximum (FWHM) decreased significantly in samples grown at lower flux ratios indicating an improvement in the optical quality.

Optimization of InxGa1−xP/In0.2Ga0.8As/GaAs high electron mobility transistor structures grown by solid source molecular beam epitaxy

A strained In0.40Ga0.60P/In0.2Ga0.8As/GaAs pseudomorphic high electron mobility transistor (PHEMT) structure was proposed to improve electron mobility. The structures were successfully grown by the solid source molecular beam epitaxy technique. Higher Hall mobility was achieved in the proposed structure, indicating that better electron distribution was formed in such a structure. Photoluminescence (PL) measurements verified that the incorporation of a strained barrier and a smoothing layer into the PHEMT structure modifies the electron distribution so that most of the electrons were distributed in the In0.2Ga0.8As channel, resulting in high electron mobility. Better device performances were also obtained in the proposed strained InxGa1−xP/In0.2Ga0.8As/GaAs PHEMT structures. These results demonstrated that strained InxGa1−xP/In0.2Ga0.8As PHEMTs are superior to the lattice-matched ones, and they are very promising candidates for microwave power applications.

Photoluminescence and electron transport properties of silicon-doped Ga/sub 0.52/In/sub 0.48/P/GaAs grown using a valved phosphorus cracker cell in solid source molecular beam epitaxy

We report the transport and photoluminescence (PL) properties of silicon-doped GaInP layers grown on GaAs[100] substrate using a valved phosphorus cracker cell in solid source molecular beam epitaxy (SSMBE). Within the range of silicon (Si) effusion cell temperature investigated (900 to 1200/spl deg/C), the highest electron concentration obtained was 7.7/spl times/10/sup 18/ cm/sup -3/ and 3.2/spl times/10/sup 18/ cm/sup -3/ at room temperature and 77 K, respectively. The concentration decreased with further increase in the silicon cell temperature. The Hall mobility at 300 K varied from 356 to 1720 cm/sup 2//Vs within the range of electron concentration measured (4.5/spl times/10/sup 16/ to 7.7/spl times/10/sup 18/ cm/sup -3/). Except for the sample grown at the highest silicon cell temperature (1200/spl deg/C), the PL spectrum of other samples showed a dominant peak attributed to Si donor-to-band transition (D-B), which shifted to higher energy following an increase in the electron concentration. This phenomenon was attributed to the Burstein-Moss effect. The blue shift of the (D-B) transition peak at increasing temperature was attributed to thermal ionization of the Si donors. The sample grown at the highest Si cell temperature showed a PL, peak at /spl sim/1.913 eV which was attributed to transition between the conduction band and Si acceptor (B-A), with an activation energy of /spl sim/57.2 meV as deduced from the PL spectrum. Temperature-dependent Hall measurements confirmed the amphoteric behaviour of the Si dopant in this sample.

Molecular beam epitaxial growth of InP using a valved phosphorus cracker cell: optimization of electrical, optical and surface morphology characteristics

We report the molecular beam epitaxial (MBE) growth of epitaxial InP using a valved phosphorous cracker cell at a range of cracking zone temperature (T/sub cr/=875/spl deg/C to 950/spl deg/C), V/III flux ratio (V/III=1.2 to 9.3) and substrate temperature (T/sub s/=360/spl deg/C to 500/spl deg/C). The as-grown epitaxial InP on InP [100] substrate was found to be n-type from Hall measurements. The background electron concentration and mobility exhibited a pronounced dependence on the cracking zone temperature, V/III flux ratio and substrate temperature. Using a cracking zone temperature of 850/spl deg/C, the highest 77 K electron mobility of 40900 cm/sup 2//Vs was achieved at a V/III ratio of 2.3 at substrate temperature (T/sub s/) of 440/spl deg/C. The corresponding background electron concentration was 1.74/spl times/10/sup 15/ cm/sup -3/. The photoluminescence (PL) spectra showed two prominent peaks at 1.384 eV and 1.415 eV, with the intensity of the low energy peak becoming stronger at higher cracking zone temperatures. The lowest PL FWHM achieved at 5 K was 5.2 meV.