K. L. Hess

High purity GaAs prepared from trimethylgallium and arsine

A study of the sources and control of residual impurities in GaAs grown by metalorganic chemical vapor deposition (MOCVD) is presented. The effects of source purity, growth temperature, and reactor pressure upon residual impurities incorporation are detailed. Far infrared photoconductivity and photoluminescence indicate that C, Si and Zn are the dominant residual impurities in undoped material. It is demonstrated that GaAs with total impurity concentrations as low as 5 × 1014 cm-3, μ(77 K) = 125,000 cm2/V · s, can be grown by MOCVD. The conditions for growing such material are detailed.

An analytical evaluation of GaAs grown with commercial and repurified trimethylgallium

An analytical study of the impurities in trimethylgallium (TMGa) and subsequent correlation of the effect of these impurities on resulting GaAs films grown by metalorganic chemical vapor deposition (MOCVD) is presented. The effects of using fractional distillation techniques to improve the quality of TMGa and to help isolate and identify major source impurities in TMGa is detailed. Photothermal ionization data are presented which show the residual donor species present and their relative concentrations in the epitaxial layers. Correlations of the residual donor concentrations with TMGa preparation are made. It is demonstrated that high purity GaAs with μ77 K ≈ 125,000 cm2/V-sec can be grown by MOCVD using repurified trimethylgallium and arsine source materials.

Integrated safety system for MOCVD laboratory

Abstract Several hazardous gases and liquids are used during the epitaxial growth of compound semiconductor materials by metalorganic chemical vapor deposition (MOCVD). The purpose of this paper is to profile the hazardous properties of two of these gases, arsine (AsH 3 ) and phosphine (PH 3 ), and summarize Rockwell MRDCs approach to the safe handling, detection, measurement and removal of these materials as they relate to MOCVD process technology.

Semi-insulating InP grown by low pressure MOCVD

Fe-doped semi-insulating InP layers have been successfully grown in a vertical flow, low pressure metalorganic chemical vapor deposition (LPMOCVD) system, and used as current blocking layers in buried crescent (BC) laser structures emitting at 1.51 µm. Triethylindium ((C2H2)3In), phosphine (PH3) and iron pentacarbonyl (Fe(CO)5) were used as the reactant gases. Process variables have been identified which produce high resistivity (107 to 108 Ω-cm) InP having featureless surface morphology, and layer thickness and doping uniformity. There is optical and x-ray diffraction evidence for the presence of an unidentified In-Fe-P second phase associated with markedly degraded surface morphology under nonoptimized growth conditions. Early BC lasers incorporating LPMOCVD grown, Fe-doped InP blocking layers have operated CW with threshold currents as low as 12 m A and optical output > 18 mW.

THE EFFECTS OF V/III RATIO AND GROWTH TEMPERATURE ON THE ELECTRICAL AND OPTICAL PROPERTIES OF InP GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL VAPOR DEPOSITION

Electrical and optical properties of InP grown by low-pressure metalorganic chemical vapor deposition using triethylindium (TEI) and phosphine (PH3) are described. It was found that the net ionized impurity concentration shows a monotonic decrease as the PH3/TEI ratio increases. Similarly, the electron mobility and the photoluminescent intensity increases with the PH3/TEI ratio. The effect of growth temperature has also been investigated in the range from 500 to 650°C. For a variety of PH3/TEI ratios, the optimal growth temperature is in the range of 550×600éC. In terms of impurities, the dominant shallow acceptors are Zn and possibly C, and the most common deep acceptor is Mn. The best material obtained shows a net electron concentration of 1 × 1015 cm−3 with an associated 77K electron mobility of 41,000 cm2 /Vsec, implying that the total ionized,impurity concentration is in the range of 34 □ 1015 cm−3

Semi-insulating cobalt doped indium phosphide grown by MOCVD

A process is described for growing at least one layer doped with a transition element of cobalt on a substrate by introducing a source of indium, such as tri ethyl indium, (C2 H5)3 In or, a source of a group V element, a source of the transition element, such as cobalt nitrosyl tricarbonyl CO(NO)(CO)3, and a source of phosphorus, to the substrate heated in an inert or reducing atmosphere at a pressure substantially between 1/100 atmosphere and one atmosphere to grow at least one semi-insulating semiconductor layer on the substrate.

Growth and characterization of Ga1−xInxAs by low pressure metalorganic chemical vapor deposition

Conditions for growth at 550°C of high structural quality GaInAs by LPMOCVD are presented. The sensitivity of compositional grading to changes in the V/III molar ratio, growth rate and inclusion of InP buffer layers is discussed. Crystalline uniformity is indicated by double crystal x-ray rocking curves with FWHM (GaInAs) = 0.017°. By careful control of the V/III molar ratio, epitaxial GaInAs/InP heterostructures with δa/a ≤ 10−4 can be grown. Quantitative data for the TEIn-AsH3 elimination reaction rate is presented. The composition of Ga1−xInxAs which is expected in the presence of this reaction is calculated; evaluation of the corresponding rate constant shows that the adduct formation reaction proceeds at a modest but detectable rate. The problems associated with the purity of electronic grade triethylindium (TEIn) are addressed. Impurities in commercial TEIn have been determined by low resolution mass spectroscopy.

Dynamic characteristics of semi‐insulating current blocking layers: Application to modulation performance of 1.3‐μm InGaAsP lasers

The dependence of current‐voltage (I‐V) characteristics on Fe‐doped semi‐insulating (SI) InP layer thickness has been investigated experimentally. The I‐V characteristics exhibit nonlinear behavior with ohmic, transition, and space‐charge‐limited regimes. An approximate circuit model of the buried crescent laser which describes the dynamic characteristics of the SI current blocking layers is presented. It is shown that for a 5‐μm‐thick SI layer, a very high resistivity of 4.9×108 Ωu2009cm and a very low capacitance of 1 pF are obtained at the typical operating voltage for laser diodes of 1–2 V. Thus, semiconductor lasers with Fe‐doped SI InP current blocking layers offer great promise for achieving both wide modulation bandwidth and high‐power operation.

Neutron transmutation doping of high‐purity InP

Transmutation doping of high‐purity n‐type InP has been used to identify the photothermal ionization photoconductivity peaks due to Sn donors. The results obtained show that Sn and S donors in InP have the same ionization energy and the same ground‐state central cell shifts within a resolution of 0.006 meV.

Laser reflectance monitoring of the nucleation and growth of CdTe on basal plane sapphire substrates for focal plane arrays

The nucleation of CdTe onto basal plane sapphire and the subsequent growth of a CdTe buffer layer has been studied using in-situ laser reflectance (probe wavelength 633 nm, HeNe laser). The production of midwave infrared focal plane arrays requires the growth of typically 10 micrometer of CdTe (111)B buffer layer in order to grow out problems due to stacking faults, dislocation clusters and twinning. A-face and B-face growth of CdTe is seen to produce different reflectance signatures within the first 6000 angstroms of growth, so enabling the early identification of problems with the growth process. Laser reflectance was also successfully demonstrated to predict the thickness of the buffer layer. Oscillations in the laser reflectance are attenuated due to absorption by the film at the probe wavelength used after approximately 6000 angstrom. However by the on-line calculation of the growth rate at every half wavelength oscillation, it is possible to extrapolate a film thickness for the total growth time. This extrapolated value is seen to be in good agreement with the thickness calculated ex-situ by beta-back scattering. The dependence on the buffer layer growth on the nucleation conditions was also investigated. The determination of whether the buffer layer grows A-face or B-face is seen to be more influenced by the II:VI ratio than the temperature during nucleation. For a nucleation temperature of 400 degrees Celsius, with a II:VI ratio of 6:1 the growth of the buffer layer is seen to be 100% A-face. As the II:VI ratio is increased the degree of A-face growth is seen to decline and the material becomes dominated by B-face growth. At a II:VI ratio of 60:1 the material is entirely B-face and predominantly untwinned. The difference in the two growth modes is manifested in the laser reflectance. Greater scattering of the laser light occurs during B-face growth due to the increased roughening compared to A-face growth. Consequently the reflectance signal in the B-face signature is seen to fall away more rapidly than is the case with A-face growth.