GaAs Whiskers Research Articles

Growth mechanism of planar-type GaAs nanowhiskers

The mechanism for the lateral growth of ultrathin GaAs whiskers is discussed in connection with the vapor–liquid–solid growth model. The observed growth rate shows that the migration of the source material plays an essential role in such whisker growth.

Growth and optical properties of nanometer-scale GaAs and InAs whiskers

The growth process, crystal structure, and optical properties of ultrathin GaAs and InAs wires (whiskers) as thin as 15–40 nm and about 2 μm long are reviewed and discussed. Experimental results for growing whiskers using Au as a growth catalyst during metalorganic vapor phase epitaxy (MOVPE) and the shape and growth direction of whiskers provide new insight into growth control of GaAs and InAs whiskers. The crystal structure of whiskers, Au behavior during MOVPE, and their growth mechanism are reviewed and discussed on the basis of transmission electron microscopic analysis. The photoluminescence spectra of GaAs wires are compared with those of a GaAs epitaxial layer, and the effect of surface treatment on the luminescence peak energy shift is discussed. The time dependent photoluminescence of GaAs wires is also discussed. The application of GaAs whiskers to light emitting devices is reviewed because a semiconductor wire structure employing quantum size effects is a very important element of electronic and optical devices.

Optical Properties of GaAs Nano-Whiskers

Nanometer-size free-standing GaAs whiskers are fabricated by selective area growth based on reduced-pressure metal-organic vapor-phase epitaxy. Photoluminescence measurements of these GaAs whiskers show a spectral blue shift due to the two-dimensional quantum confinement of the carriers. The spectral blue shift is, however, much smaller than the lowest level energy expected by the square-potential confinement. This is due to a band-gap reduction induced by the charge separation caused by the existence of surface depletion potential, which is confirmed by surface passivation experiments using sulfur compounds. Furthermore, intense light emission is observed during carrier injection to the p-n junction formed in the GaAs whisker. The emitted light shows strong polarization anisotropy, which can be explained by the quantum confinement effect. These results indicate that nano-whiskers offer high-quality quantum wire structures, which can be applied to ultra-small opto-electronic devices.

Nanocolumns composed of GaAs-InAs jointed whiskers and SiO2 covers

A dense array of nanocolumns composed of GaAs-InAs jointed whiskers and SiO2 covers has been fabricated on InAs substrates. The cylindrical GaAs whisker with a 20 nm diameter and 1.5 μm long is jointed on top of 0.3-μm-long InAs whisker by vapor-liquid-solid epitaxy. The nanocolumns array exhibited photoluminescence at 14 K.

Crystal Structure Change of GaAs and InAs Whiskers from Zinc-Blende to Wurtzite Type

Crystal structures of GaAs and InAs whiskers grown by metalorganic vapor phase epitaxy are evaluated by means of a transmission electron microscope. The whiskers are grown epitaxially on GaAs substrates with diameters of 20-100 nm and lengths of 1-5 µm. They have the following characteristics. 1) GaAs whiskers have layered structures with 2-30 nm period, that are the 111 rotating twins of the zinc-blende type. 2) InAs whiskers also have layered structures which consist of wurtzite and zinc-blende type crystals. The wurtzite type InAs is observed for the first time in this study. The volume ratio of these two types strongly depends on the growth conditions, such as substrate temperature and material gas pressure. This suggests that defect-free whiskers with a single phase that are useful for quantum wire devices can be grown by controlling the growth conditions.

PULSE LASER ATOM PROBE STUDY OF GaP

Gap tips prepared f ran whiskers grown by the vapour phase reaction, were analyzed using our ctmbined-type atom-probe FIM by laser pulse operation instead of high voltage pulse operation. It was found that ( 1 ) The mposition is Ga : P=l : l at cryogenic temperature 45K in vacuum of better than 1 x 10-Ptorr. ( 2 ) Much more cluster ions of phosphorus atan in laser pulse mode are detected in canparison to that in high voltage pulse mode. (3) Mass resolution for laser pulse operation is high enough to resolved the hydride ions even at linear type mode. We also make clear the influences of laser beam power density irradiated on the tip for field evaporation. The TOF atcan-probe technique has only been applied to metallic samples due to the difficulty to transmit the nano-second high-voltage pulse through sample tips of low electrical conductivity. Another problem is distortion or reflection of high voltage pulse which result in anenergy spread of the fieXd eeMprated ions. Kellogg and Tsong proved that laser-assisted field evaporation can be used for TOF atom probe operation / l / . Using laser pulses, as v e d to high-voltage pulses, for TOF atan-probe operation eleiminates the above-mentioned problems and gives applicability to low-conductivity materials. The field evaporation of silicon in ultrahigh vacuum and at cryogenic temperature is qualitatively the same as for metal /2/, /3/. Recently, Cerezo et a1 show a pulse laser atan probe (PLAP) /l / mass spectrum for a GaAs whisker, giving a stoichimtry of &/AS = 0.99 0.03 /4/. They also give that the value obtained for Inks whisker is In/& = 0.97 + 0.05 /4/. We have also done nearly the same experiment for Gap whisker. As the sample of the atom probe, GaP whiskers withfhe [TT71 growth orientation were used in the same m e r as the previous experiments /5/. The resistivity of GaP was estimated to be more than 0.004nan. The sharp emitters of GaPwereprepared by dipping the specimens for a few minites in the hot solution of HNOj : HC1 (1 : 3). Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1986244

GaAs whiskers grown by a thermal decomposition method

Gallium arsenide whiskers have been grown on GaAs substrate by a thermal decomposition method using AsH 3 and trimethyl gallium (or triethyl gallium). The whiskers were single crystal hexagonal needles with [111] growth direction and (110) lateral faces. A new morphology was observed near the tip of the whiskers. The whiskers had feeler-like micro whiskers at the tip and had many humps on the side faces near the tip. The results of electron probe micro analysis suggested that there existed a gallium droplet at the tip of the whiskers during the growth. The growth mechanism of the whiskers was concluded to be basically the vapor-liquid-solid mechanism.

Oriented growth of whiskers of AIIIBV compounds by VLS‐mechanism

AbstractThe oriented growth of GaAs, GaP, InAs and GaInAs whiskers on the same (GaAs, GaP) or different (InAs/GaAs, GaInAs/GaAs) substrates was studied. A detailed morphological study of GaAs whiskers on polar A(III), B(111) and non‐polar (001), (011) substrates was performed. The growth conditions for ordered (perpendicular to substrate) growth on the A(111) and B(111) faces were determined. There were found discrete spectra of whisker systems on all substrates with the preferential growth of “arsenic” B{111} faces. The dependence of the growth rate on the whisker diameter is typical for the vapour‐liquid‐solid (VLS) mechanism and is used for the determination of kinetic coefficients for polar faces. There was observed a periodic instability in growth of InAs and GaInAs whiskers.

A survey of precision lattice parameter measurements as a tool for the characterization of single-crystal materials

Bond's method of measuring the lattice parameter of single crystals has been improved and the Bragg angle can be readily measured with a probable error of 0.5 arc secs. Ignoring the wavelength uncertainty, this gives the lattice parameter (averaged over the diffracting volume) for many materials to a probable error of 0.5 ppm. The diffracting volume can be as small as 0.5×0.02×0.005 mm. Results of measurements on Si, GaAs whiskers, K(Ta xNb 1−x)O 3 and KTaO 3 are shown as examples of the use of lattice parameter measurements for the characterization of materials.