High Purity GaAs Layers Research Articles

New apparatus with double supersonic molecular beams for epitaxial growth and surface reaction studies

To understand surface reaction dynamics in III–V compound semiconductor growth, we have developed an apparatus to study both surface chemical reactions and epitaxial growth. This apparatus has double supersonic III and V compound molecular beam cells and an analytical chamber with a rotatable differentially pumped liquid-nitrogen-cooled quadrupole mass spectrometer to measure angular and time-of-flight distribution of reflected beams. It also has reflection high-energy electron diffraction to analyze surface structures. Tertiarybutylarsine beam energies of 1.6 eV were obtained for He, 0.22 eV for Ar, and 0.06 eV for Xe seeding. An organometallic molecular beam of translational energy is varied over a wide range, enabling source molecules to be brought to a well-defined epitaxial surface in well-characterized ways. High-purity GaAs layers were grown by alternatively supplying triethylgallium and tertiarybutylarsine molecules to the analytical chamber. Our apparatus bridges the gap of studies between epitaxial growth and surface chemical reactions. Dynamic measurement on the growth surface revealed a number of interesting reactions not ordinarily observed on well-defined surfaces.

Residual impurities in high purity GaAs layers grown by liquid phase epitaxy in H 2–Ar atmosphere

We have carried out LPE of GaAs using Ga as a solvent in high purity Ar and its mixture with H 2. The quality of the layers was compared with that grown in pure H 2. The layers grown in Ar showed n-type conductivity. Net carrier concentration and mobility were 3×10 14 cm −3 and 4×10 4 cm 2 V −1 s −1 at 77 K which is comparable to that for the layers grown in H 2. Photoluminescence measurements reveal that Si is the main acceptor impurity in GaAs layers which were grown in H 2 atmosphere. In contrast, C is the main impurity in the layers grown in Ar atmosphere. The impurity incorporation into GaAs layers can be ascribed to the chemical reactions that take place during the LPE process in the growth system which consists of quartz reactor tube, graphite crucible, and Ga solvent.

Growth of High Purity GaAs Layers by Vapour Phase Epitaxy

Growth of High Purity GaAs Layers by Vapour Phase Epitaxy

Narrowband Landau emission from high purity GaAs layers grown by molecular beam epitaxy

We analysed narrowband Landau emission from a high purity GaAs layer grown by molecular beam epitaxy using a magnetic field tuned InSb detector. The cyclotron resonance and impurity level transitions of the InSb detector are clearly resolved. Comparison of the detector linewidth with results from a fast Fourier transform spectrometer yields a narrow GaAs emitter linewidth of 1.3 ± 0.3 cm −1 which is in good agreement with cyclotron resonance transmission data. This indicates very high quality of the GaAs material with very low impurity compensation. Only two types of impurity, silicon and sulphur, are detected in the extrinsic photoresponse spectrum.

Arsine flow requirement for the flow modulation growth of high purity GaAs using adduct-grade triethylgallium

Using arsine and triethylgallium with flow modulation, organometallic vapor phase epitaxy can produce high purity GaAs layers with V/III molar ratios near unity. We have estimated that under appropriate growth conditions the arsine incorporation efficiency into epitaxial GaAs can exceed 30%. The arsine flow requirement for obtaining good morphology has been identified over a range of substrate temperatures using adduct-grade triethylgallium. The process described reduces the environmental impact and life safety risk of the hydride based organometallic vapor phase epitaxial method.

Control of residual impurities in very high purity GaAs grown by organometallic vapor phase epitaxy

Very high purity GaAs layers with 77 K electron mobility values as high as 210 000 cm2/V s and a compensation ratio as low as ≊0.05 (NA+ND≊1014 cm−3) have been grown by organometallic vapor phase epitaxy. 4.2 K photoluminescence and magnetophotoluminescence spectra of these layers confirm their high purity. The degree of material purity and the compensation are found to be controllably dependent on the growth conditions, the optimum growth temperature being about 650 °C at a V:III ratio of 17.5.

High Purity Epitaxial GaAs

Using the AsCl3-Ga-H2 vapor phase epitaxial system, high purity GaAs layers with liquid nitrogen mobilities in the range of 1.8 to 2.1×105 cm2/V.s and carrier concentrations in the range of 2.0 to 5.3×1013/cm3 are obtained with good reproducibility. Mobilities tend to decrease with decreasing layer thickness. AsCl3 mole flux versus the log of carrier concentration at 77K shows a linear relationship. Details of the growth apparatus and the growth procedures are presented.

The Influence of Oxygen on the Properties of GaAs Grown by Liquid Phase Epitaxy

Epitaxial layers of GaAs are grown from Ga solution. The effects of oxygen in achieving high purity GaAs layers are investigated. From the experimental results of doping with Ga2O3, the growth temperature dependence of carrier concentration and the impurity profile are explained by the temperature dependence of the distribution coefficient of oxygen in GaAs grown by liquid phase epitaxy. The distribution coefficients of oxygen are 6.5×10-4 at 700°C, 1.8×10-4 at 750°C and 5.1×10-5 at 800°C, respectively.